Compute the variance of an array, ignoring NaNs.

        :param a: The array.
        :return: The variance of the array.

def fn_var(self, a, axis=None):
        """
        Compute the variance of an array, ignoring NaNs.

        :param a: The array.
        :return: The variance of the array.
        """

        return numpy.nanvar(self._to_ndarray(a), axis=axis)