src/transformers/pipelines/conversational.py/ConversationalPipeline/__call__
class ConversationalPipeline:    def __call__(self, conversations: Union[Conversation, List[Conversation]], num_workers=0, **kwargs):
        r"""
        Generate responses for the conversation(s) given as inputs.

        Args:
            conversations (a :class:`~transformers.Conversation` or a list of :class:`~transformers.Conversation`):
                Conversations to generate responses for.
            clean_up_tokenization_spaces (:obj:`bool`, `optional`, defaults to :obj:`False`):
                Whether or not to clean up the potential extra spaces in the text output.
            generate_kwargs:
                Additional keyword arguments to pass along to the generate method of the model (see the generate method
                corresponding to your framework `here <./model.html#generative-models>`__).

        Returns:
            :class:`~transformers.Conversation` or a list of :class:`~transformers.Conversation`: Conversation(s) with
            updated generated responses for those containing a new user input.
        """
        # XXX: num_workers==0 is required to be backward compatible
        # Otherwise the threads will require a Conversation copy.
        # This will definitely hinder performance on GPU, but has to be opted
        # in because of this BC change.
        outputs = super().__call__(conversations, num_workers=num_workers, **kwargs)
        if isinstance(outputs, list) and len(outputs) == 1:
            return outputs[0]
        return outputs