code: def read(self):
          # type: () -> Optional[str]
          
          with open(self.version_file) as fp:
              content = fp.read()
              m = RE_PY_VERSION.search(content)
              if not m:
                  return None
              else:
                  return m.group('version')
docs: Read the project version from .py file.
  
          This will regex search in the file for a
          ``__version__ = VERSION_STRING`` and read the version string.