'initialize instance
Parameters
mean : array_like
parameter mu (might be renamed), for symmetric distributions this
is the mean
sigma : array_like, 2d
dispersion matrix, covariance matrix in normal distribution, but
only proportional to covariance matrix in t distribution
args : list
distribution specific arguments, e.g. df for t distribution
kwds : dict
currently not used'

def __init__(self, mean, sigma, df):

    super(MVT, self).__init__(mean, sigma)
    self.extra_args = ['df']
    self.df = df
