How to use the fastecdsa.encoding.der.DEREncoder.encode_signature function in fastecdsa

def der_encode_sig(r, s):
    """
    Create DER encoded signature string with signature r and s value

    :param r: r value of signature
    :type r: int
    :param s: s value of signature
    :type s: int

    :return bytes:
    """
    if USE_FASTECDSA:
        return DEREncoder.encode_signature(r, s)
    else:
        rb = ecdsa.der.encode_integer(r)
        sb = ecdsa.der.encode_integer(s)
        return ecdsa.der.encode_sequence(rb, sb)