docs: def upload_file(self, fax_file, **kwargs):  # noqa: E501
          """upload a file  # noqa: E501
  
          Before sending a fax you need to upload your files using this API. In order to upload your fax file, you have to send a `multipart/form-data` request with your file. If the upload was successful you would receive a `file_path` which you can use to send your fax.  # noqa: E501
          This method makes a synchronous HTTP request by default. To make an
          asynchronous HTTP request, please pass async=True
          >>> thread = api.upload_file(fax_file, async=True)
          >>> result = thread.get()
  
          :param async bool
          :param file fax_file: (required)
          :param str format: can be 'pdf' or 'tiff'
          :return: File
                   If the method is called asynchronously,
                   returns the request thread.
          """
          kwargs['_return_http_data_only'] = True
          if kwargs.get('async'):
              return self.upload_file_with_http_info(fax_file, **kwargs)  # noqa: E501
          else:
              (data) = self.upload_file_with_http_info(fax_file, **kwargs)  # noqa: E501
              return data