Returns True if dict_id not already used.  Otherwise, invokes error

def id_unique(dict_id, name, lineno):
    """Returns True if dict_id not already used.  Otherwise, invokes error"""
    if dict_id in name_dict:
        global error_occurred
        error_occurred = True
        print(
            "ERROR - {0:s} definition {1:s} at line {2:d} conflicts with {3:s}"
            .format(name, dict_id, lineno, name_dict[dict_id]))
        return False
    else:
        return True