Add Python interface to __init__ and instruction to README.

README.md

@@ -125,6 +125,8 @@ $ pip install stubdoc
 
 # Usage
 
+Notes: specified module need to be able to import. Stubdoc will replace paths to package path (e.g., 'sample/path.py' to 'sample.path'), so that paths argument can not be specified upper level directory or root directory (e.g., '/sample/path.py' or '../sample/path').
+
 ```
 This command will add docstring to stub file. Currently supported one-line stub implementation, like mypy's stubgen
 command, something as follows: def any_func(a: int, b: str) -> None: ... If line break exists after colon, this
@@ -150,6 +152,16 @@ or
 $ stubdoc --module_path samples/sample.py --stub_path out/samples/sample.pyi
 ```
 
+Or maybe Python interface is useful, like Django environment:
+
+```py
+from stubdoc import add_docstring_to_stubfile
+
+add_docstring_to_stubfile(
+    original_module_path='sample/path.py',
+    stub_file_path='sample/path.pyi')
+```
+
 # Limitations
 
 This library supported only one-line stub implementation, like this:

development_doc.md

@@ -32,7 +32,7 @@ $ poetry run pytest --cov=./ tests/ -v -s -k <module_or_func_name>
 Notes: this command maybe hang-up on Windows. In that case it is necessary to press Ctrl + C to stop.
 
 ```
-$ stubgen --include-private ./
+$ poetry run stubgen --include-private ./
 ```
 
 # Try to apply stubdoc to generated stub

stubdoc/__init__.py

@@ -1 +1,2 @@
 __version__: str = '0.1.5'
+from stubdoc.stubdoc import add_docstring_to_stubfile