def check_attr(_attr):
    """
    Check the _attr dictionary when creating a new table.
    Legal properties are ['NotNull','Unique','AutoIncrease'].
    """
    if not isinstance(_attr, dict):
        return False
    for k, v in _attr.items():
        if not isinstance(v, list):
            return False
        for i in v:
            if i not in ['NotNull', 'Unique', 'AutoIncrease']:
                return False
    return True
