def is_abs(field):
    """
    Check if field is absolute value.

    Parameters
    ----------
    field : str
        Field name.

    Returns
    -------
    (bool, str)
        Whether the field is absolute or not along with the basic field itself.
    """

    if field[:4] == 'ABS(' and field[-1] == ')':
        return field[4:-1], True
    else:
        return field, False