Exclude topics with the indices `excl_topic_indices` from the document-topic distribution `doc_topic_distrib` (i.e.
    delete the respective columns in this matrix) and optionally re-normalize the distribution so that the rows sum up
    to 1 if `renormalize` is set to `True`.
    Optionally also strip the topics from the topic-word distribution `topic_word_distrib` (i.e. remove the respective
    rows).

    If `topic_word_distrib` is given, return a tuple with the updated doc.-topic and topic-word distributions, else
    return only the updated doc.-topic distribution.

    *WARNING:* The topics to be excluded are specified by *zero-based indices*.

def exclude_topics(excl_topic_indices, doc_topic_distrib, topic_word_distrib=None, renormalize=True,
                   return_new_topic_mapping=False):
    """
    Exclude topics with the indices `excl_topic_indices` from the document-topic distribution `doc_topic_distrib` (i.e.
    delete the respective columns in this matrix) and optionally re-normalize the distribution so that the rows sum up
    to 1 if `renormalize` is set to `True`.
    Optionally also strip the topics from the topic-word distribution `topic_word_distrib` (i.e. remove the respective
    rows).

    If `topic_word_distrib` is given, return a tuple with the updated doc.-topic and topic-word distributions, else
    return only the updated doc.-topic distribution.

    *WARNING:* The topics to be excluded are specified by *zero-based indices*.
    """
    new_theta = np.delete(doc_topic_distrib, excl_topic_indices, axis=1)
    if renormalize:
        new_theta /= new_theta.sum(axis=1)[:, None]

    if topic_word_distrib is not None:
        new_phi = np.delete(topic_word_distrib, excl_topic_indices, axis=0)
        res_tuple = (new_theta, new_phi)
    else:
        res_tuple = (new_theta, )

    if return_new_topic_mapping:
        topic_ind = np.arange(doc_topic_distrib.shape[1])
        old_topic_ind = np.delete(topic_ind, excl_topic_indices)
        res_tuple += (dict(zip(old_topic_ind, range(len(old_topic_ind)))), )

    if len(res_tuple) == 1:
        return res_tuple[0]
    else:
        return res_tuple