def _createShapelet(self, coeffs):
        """
        returns a shapelet array out of the coefficients *a, up to order l

        :param num_l: order of shapelets
        :type num_l: int.
        :param coeff: shapelet coefficients
        :type coeff: floats
        :returns:  complex array
        :raises: AttributeError, KeyError
        """
        n_coeffs = len(coeffs)
        num_n = self._get_num_n(n_coeffs)
        shapelets=np.zeros((num_n+1, num_n+1))
        n = 0
        k = 0
        for coeff in coeffs:
            shapelets[n-k][k] = coeff
            k += 1
            if k == n + 1:
                n += 1
                k = 0
        return shapelets