input: Write a python function to convert a string to a Python string.
  assert _to_python_str(b'hello') == 'hello'
  assert _to_python_str('world') == 'world'
  assert _to_python_str(b'12345') == '12345'
output: def _to_python_str(input_data):
      if isinstance(input_data, bytes):
          return input_data.decode('utf-8')
      return input_data