Replace string with str in rtypes.

Used the command:
ag -l 'rtype: string' | xargs sed -i .bak 's/rtype: string/rtype: str/g'

Based on this comment:
googleapis#2485 (comment)

`str` is a type, `string` is a module.

bigquery/google/cloud/bigquery/dataset.py

@@ -115,7 +115,7 @@ def __init__(self, name, client, access_grants=()):
     def project(self):
         """Project bound to the dataset.
 
-        :rtype: string
+        :rtype: str
         :returns: the project (derived from the client).
         """
         return self._client.project
@@ -124,7 +124,7 @@ def project(self):
     def path(self):
         """URL path for the dataset's APIs.
 
-        :rtype: string
+        :rtype: str
         :returns: the path based on project and dataste name.
         """
         return '/projects/%s/datasets/%s' % (self.project, self.name)
@@ -168,7 +168,7 @@ def created(self):
     def dataset_id(self):
         """ID for the dataset resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the ID (None until set from the server).
         """
         return self._properties.get('id')
@@ -177,7 +177,7 @@ def dataset_id(self):
     def etag(self):
         """ETag for the dataset resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the ETag (None until set from the server).
         """
         return self._properties.get('etag')
@@ -198,7 +198,7 @@ def modified(self):
     def self_link(self):
         """URL for the dataset resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the URL (None until set from the server).
         """
         return self._properties.get('selfLink')
@@ -229,7 +229,7 @@ def default_table_expiration_ms(self, value):
     def description(self):
         """Description of the dataset.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: The description as set by the user, or None (the default).
         """
         return self._properties.get('description')
@@ -251,7 +251,7 @@ def description(self, value):
     def friendly_name(self):
         """Title of the dataset.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: The name as set by the user, or None (the default).
         """
         return self._properties.get('friendlyName')
@@ -273,7 +273,7 @@ def friendly_name(self, value):
     def location(self):
         """Location in which the dataset is hosted.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: The location as set by the user, or None (the default).
         """
         return self._properties.get('location')

bigquery/google/cloud/bigquery/job.py

@@ -96,7 +96,7 @@ def __init__(self, client):
     def project(self):
         """Project bound to the job.
 
-        :rtype: string
+        :rtype: str
         :returns: the project (derived from the client).
         """
         return self._client.project
@@ -135,7 +135,7 @@ def __init__(self, name, client):
     def job_type(self):
         """Type of job
 
-        :rtype: string
+        :rtype: str
         :returns: one of 'load', 'copy', 'extract', 'query'
         """
         return self._JOB_TYPE
@@ -144,7 +144,7 @@ def job_type(self):
     def path(self):
         """URL path for the job's APIs.
 
-        :rtype: string
+        :rtype: str
         :returns: the path based on project and job name.
         """
         return '/projects/%s/jobs/%s' % (self.project, self.name)
@@ -153,7 +153,7 @@ def path(self):
     def etag(self):
         """ETag for the job resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the ETag (None until set from the server).
         """
         return self._properties.get('etag')
@@ -162,7 +162,7 @@ def etag(self):
     def self_link(self):
         """URL for the job resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the URL (None until set from the server).
         """
         return self._properties.get('selfLink')
@@ -171,7 +171,7 @@ def self_link(self):
     def user_email(self):
         """E-mail address of user who submitted the job.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the URL (None until set from the server).
         """
         return self._properties.get('user_email')
@@ -241,7 +241,7 @@ def errors(self):
     def state(self):
         """Status of the job.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the state (None until set from the server).
         """
         status = self._properties.get('status')

bigquery/google/cloud/bigquery/query.py

@@ -91,7 +91,7 @@ def from_query_job(cls, job):
     def project(self):
         """Project bound to the job.
 
-        :rtype: string
+        :rtype: str
         :returns: the project (derived from the client).
         """
         return self._client.project
@@ -185,7 +185,7 @@ def page_token(self):
         See:
         https://cloud.google.com/bigquery/docs/reference/v2/jobs/query#pageToken
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: Token generated on the server (None until set by the server).
         """
         return self._properties.get('pageToken')

core/google/cloud/_helpers.py

@@ -526,7 +526,7 @@ def _pb_timestamp_to_rfc3339(timestamp_pb):
     :type timestamp_pb: :class:`google.protobuf.timestamp_pb2.Timestamp`
     :param timestamp_pb: A Google returned timestamp protobuf.
 
-    :rtype: string
+    :rtype: str
     :returns: An RFC 3339 formatted timestamp string.
     """
     timestamp = _pb_timestamp_to_datetime(timestamp_pb)

core/google/cloud/connection.py

@@ -179,7 +179,7 @@ def build_api_url(cls, path, query_params=None,
                             Typically you shouldn't provide this and instead
                             use the default for the library.
 
-        :rtype: string
+        :rtype: str
         :returns: The URL assembled from the pieces provided.
         """
         url = cls.API_URL_TEMPLATE.format(

core/google/cloud/credentials.py

@@ -220,7 +220,7 @@ def generate_signed_url(credentials, resource, expiration,
     :param generation: (Optional) A value that indicates which generation of
                        the resource to fetch.
 
-    :rtype: string
+    :rtype: str
     :returns: A signed URL you can use to access the resource
               until expiration.
     """

core/google/cloud/streaming/transfer.py

@@ -163,7 +163,7 @@ def stream(self):
     def url(self):
         """URL to / from which data is downloaded/uploaded.
 
-        :rtype: string
+        :rtype: str
         :returns: The URL where data is sent/received.
         """
         return self._url
@@ -318,7 +318,7 @@ def total_size(self):
     def encoding(self):
         """'Content-Encoding' used to transfer the file
 
-        :rtype: string or None
+        :rtype: str or None
         :returns: The encoding of the downloaded content.
         """
         return self._encoding
@@ -732,7 +732,7 @@ def complete(self):
     def mime_type(self):
         """MIMEtype of the file being uploaded.
 
-        :rtype: string
+        :rtype: str
         :returns: The mime-type of the upload.
         """
         return self._mime_type
@@ -750,7 +750,7 @@ def progress(self):
     def strategy(self):
         """Upload strategy to use
 
-        :rtype: string or None
+        :rtype: str or None
         :returns: The strategy used to upload the data.
         """
         return self._strategy
@@ -972,7 +972,7 @@ def _get_range_header(response):
         :type response: :class:`google.cloud.streaming.http_wrapper.Response`
         :param response: response to be queried
 
-        :rtype: string
+        :rtype: str
         :returns: The header used to determine the bytes range.
         """
         # NOTE: Per RFC 2616[1]/7233[2][3], 'Range' is a request header,

datastore/google/cloud/datastore/client.py

@@ -53,7 +53,7 @@ def _determine_default_project(project=None):
     :type project: string
     :param project: Optional. The project to use as default.
 
-    :rtype: string or ``NoneType``
+    :rtype: str or ``NoneType``
     :returns: Default project if it can be determined.
     """
     if project is None:

datastore/google/cloud/datastore/connection.py

@@ -76,7 +76,7 @@ def _request(self, project, method, data):
         :param data: The data to send with the API call.
                      Typically this is a serialized Protobuf string.
 
-        :rtype: string
+        :rtype: str
         :returns: The string response content from the API call.
         :raises: :class:`google.cloud.exceptions.GoogleCloudError` if the
                  response code is not 200 OK.

datastore/google/cloud/datastore/key.py

@@ -269,7 +269,7 @@ def is_partial(self):
     def namespace(self):
         """Namespace getter.
 
-        :rtype: string
+        :rtype: str
         :returns: The namespace of the current key.
         """
         return self._namespace
@@ -298,7 +298,7 @@ def flat_path(self):
     def kind(self):
         """Kind getter. Based on the last element of path.
 
-        :rtype: string
+        :rtype: str
         :returns: The kind of the current key.
         """
         return self.path[-1]['kind']
@@ -316,7 +316,7 @@ def id(self):
     def name(self):
         """Name getter. Based on the last element of path.
 
-        :rtype: string
+        :rtype: str
         :returns: The (string) name of the key.
         """
         return self.path[-1].get('name')
@@ -335,7 +335,7 @@ def id_or_name(self):
     def project(self):
         """Project getter.
 
-        :rtype: string
+        :rtype: str
         :returns: The key's project.
         """
         return self._project
@@ -391,7 +391,7 @@ def _validate_project(project, parent):
     :type parent: :class:`google.cloud.datastore.key.Key` or ``NoneType``
     :param parent: The parent of the key or ``None``.
 
-    :rtype: string
+    :rtype: str
     :returns: The ``project`` passed in, or implied from the environment.
     :raises: :class:`ValueError` if ``project`` is ``None`` and no project
              can be inferred from the parent.

datastore/google/cloud/datastore/query.py

@@ -109,7 +109,7 @@ def project(self):
     def namespace(self):
         """This query's namespace
 
-        :rtype: string or None
+        :rtype: str or None
         :returns: the namespace assigned to this query
         """
         return self._namespace or self._client.namespace
@@ -128,7 +128,7 @@ def namespace(self, value):
     def kind(self):
         """Get the Kind of the Query.
 
-        :rtype: string
+        :rtype: str
         :returns: The kind for the query.
         """
         return self._kind

datastore/google/cloud/datastore/transaction.py

@@ -100,7 +100,7 @@ def __init__(self, client):
     def id(self):
         """Getter for the transaction ID.
 
-        :rtype: string
+        :rtype: str
         :returns: The ID of the current transaction.
         """
         return self._id

dns/google/cloud/dns/changes.py

@@ -74,7 +74,7 @@ def _set_properties(self, resource):
     def path(self):
         """URL path for change set APIs.
 
-        :rtype: string
+        :rtype: str
         :returns: the path based on project, zone, and change set names.
         """
         return '/projects/%s/managedZones/%s/changes/%s' % (
@@ -84,7 +84,7 @@ def path(self):
     def name(self):
         """Name of the change set.
 
-        :rtype: string or ``NoneType``
+        :rtype: str or ``NoneType``
         :returns: Name, as set by the back-end, or None.
         """
         return self._properties.get('id')
@@ -104,7 +104,7 @@ def name(self, value):
     def status(self):
         """Status of the change set.
 
-        :rtype: string or ``NoneType``
+        :rtype: str or ``NoneType``
         :returns: Status, as set by the back-end, or None.
         """
         return self._properties.get('status')

dns/google/cloud/dns/zone.py

@@ -81,7 +81,7 @@ def from_api_repr(cls, resource, client):
     def project(self):
         """Project bound to the zone.
 
-        :rtype: string
+        :rtype: str
         :returns: the project (derived from the client).
         """
         return self._client.project
@@ -90,7 +90,7 @@ def project(self):
     def path(self):
         """URL path for the zone's APIs.
 
-        :rtype: string
+        :rtype: str
         :returns: the path based on project and dataste name.
         """
         return '/projects/%s/managedZones/%s' % (self.project, self.name)
@@ -117,7 +117,7 @@ def name_servers(self):
     def zone_id(self):
         """ID for the zone resource.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: the ID (None until set from the server).
         """
         return self._properties.get('id')
@@ -126,7 +126,7 @@ def zone_id(self):
     def description(self):
         """Description of the zone.
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: The description as set by the user, or None (the default).
         """
         return self._properties.get('description')
@@ -153,7 +153,7 @@ def name_server_set(self):
         See:
         https://cloud.google.com/dns/api/v1/managedZones#nameServerSet
 
-        :rtype: string, or ``NoneType``
+        :rtype: str, or ``NoneType``
         :returns: The name as set by the user, or None (the default).
         """
         return self._properties.get('nameServerSet')