docs: def user_sentiments_most_frequent(
          self,
          username             = None,
          single_most_frequent = True
          ):
          """
          This function returns the most frequent calculated sentiments expressed
          in tweets of a specified user. By default, the single most frequent
          sentiment is returned. All sentiments with their corresponding
          frequencies can be returned also.
          """
          try:
              sentiment_frequencies = collections.Counter(self.user_sentiments(
                  username = username
              ))
              if single_most_frequent:
                  return sentiment_frequencies.most_common(1)[0][0]
              else:
                  return dict(sentiment_frequencies)
          except:
              log.error("error -- possibly no username specified")
              return None