'Parameters
dim : int
Dimension of the scale matrix
%(_doc_default_callparams)s
Notes
As this function does no argument checking, it should not be
called directly; use \'var\' instead.'

def _var(self, dim, df, scale):

    if (df > (dim + 3)):
        var = (((df - dim) + 1) * (scale ** 2))
        diag = scale.diagonal()
        var += (((df - dim) - 1) * np.outer(diag, diag))
        var /= (((df - dim) * (((df - dim) - 1) ** 2)) * ((df - dim) - 3))
    else:
        var = None
    return var
