def id_is_int(patient_id):
    """ Check if patient id is integer

    Check if the patient's id is a integer

    Args:
        patient_id (int): id number of the patient

    Returns:
        True or str: indicate if the input patient id is an integer

    """
    try:
        int(patient_id)
        return True
    except ValueError:
        return "Please use an integer or a numeric string containing " \
           "an ID number but without any letter"