a few type improvements, mostly flight related (#90)

* FlightError.extra_info -> bytes

* annotate FlightStreamReader.cancel return

* BasicAuth serialize/deserialize

* RecordBatchFileReader.schema

* actually str | bytes

pyarrow-stubs/__lib_pxi/ipc.pyi

@@ -154,6 +154,8 @@ class _RecordBatchFileReader(_Weakrefable):
     def __enter__(self) -> Self: ...
     def __exit__(self, exc_type, exc_val, exc_tb): ...
     @property
+    def schema(self) -> Schema: ...
+    @property
     def stats(self) -> ReadStats: ...
 
 def get_tensor_size(tensor: Tensor) -> int: ...

pyarrow-stubs/_flight.pyi

@@ -37,7 +37,7 @@ class CertKeyPair(NamedTuple):
     key: str
 
 class FlightError(Exception):
-    extra_info: str
+    extra_info: bytes
 
 class FlightInternalError(FlightError, ArrowException): ...
 class FlightTimedOutError(FlightError, ArrowException): ...
@@ -83,6 +83,9 @@ class BasicAuth(_Weakrefable):
     def username(self) -> bytes: ...
     @property
     def password(self) -> bytes: ...
+    def serialize(self) -> str: ...
+    @staticmethod
+    def deserialize(serialized: str | bytes) -> BasicAuth: ...
 
 class DescriptorType(enum.Enum):
     UNKNOWN = 0
@@ -196,7 +199,7 @@ class _MetadataRecordBatchReader(_Weakrefable, _ReadPandasMixin):
 class MetadataRecordBatchReader(_MetadataRecordBatchReader): ...
 
 class FlightStreamReader(MetadataRecordBatchReader):
-    def cancel(self): ...
+    def cancel(self) -> None: ...
     def read_all(self) -> Table: ...
 
 class MetadataRecordBatchWriter(_CRecordBatchWriter):