Call this in a @token_operation-decorated method.
    Identifies the account to be debited

def token_operation_put_account_payment_info(token_op, account_addr, token_type, amount):
    """
    Call this in a @token_operation-decorated method.
    Identifies the account to be debited
    """
    assert isinstance(amount, (int,long)), "BUG: amount is {} (type {})".format(amount, type(amount))
    assert isinstance(account_addr, (str,unicode)), 'BUG: account is {} (type {})'.format(account_addr, type(account_addr))
    assert isinstance(token_type, (str,unicode)), 'BUG: token_type is {} (type {})'.format(token_type, type(token_type))
    token_op['__account_payment_info__'] = {
            'address': str(account_addr),
            'type': str(token_type),
            'amount': int(amount)
    }