Creates an instance of a Gamma Prior  by specifying the Expected value(s)
        and Variance(s) of the distribution.

        :param E: expected value
        :param V: variance

def from_EV(E, V):
        """
        Creates an instance of a Gamma Prior  by specifying the Expected value(s)
        and Variance(s) of the distribution.

        :param E: expected value
        :param V: variance
        """
        a = np.square(E) / V
        b = E / V
        return Gamma(a, b)