'Return the sample with the greatest number of outcomes in this
frequency distribution.  If two or more samples have the same
number of outcomes, return one of them; which sample is
returned is undefined.  If no outcomes have occurred in this
frequency distribution, return None.
:return: The sample with the maximum number of outcomes in this
frequency distribution.
:rtype: any or None'

def max(self):

    if (len(self) == 0):
        raise ValueError(u'A    FreqDist    must    have    at    least    one    sample    before    max    is    defined.')
    return self.most_common(1)[0][0]
