code: def _get_upload_arguments(self, content_type):
          
          headers = _get_encryption_headers(self._encryption_key)
          object_metadata = self._get_writable_metadata()
          content_type = self._get_content_type(content_type)
          return headers, object_metadata, content_type
docs: Get required arguments for performing an upload.
  
          The content type returned will be determined in order of precedence:
  
          - The value passed in to this method (if not :data:`None`)
          - The value stored on the current blob
          - The default value ('application/octet-stream')
  
          :type content_type: str
          :param content_type: Type of content being uploaded (or :data:`None`).
  
          :rtype: tuple
          :returns: A triple of
  
                    * A header dictionary
                    * An object metadata dictionary
                    * The ``content_type`` as a string (according to precedence)