Calculate the checksum(s) of the d_signal (expanded=False)
        or e_d_signal field (expanded=True)

def calc_checksum(self, expanded=False):
        """
        Calculate the checksum(s) of the d_signal (expanded=False)
        or e_d_signal field (expanded=True)
        """
        if expanded:
            cs = [int(np.sum(self.e_d_signal[ch]) % 65536) for ch in range(self.n_sig)]
        else:
            cs = np.sum(self.d_signal, 0) % 65536
            cs = [int(c) for c in cs]
        return cs