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.

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