def get_properties(schema):
    """ Return the three properties we have to enforce for this schema.
    Returns tuple of (enforce, default, and required), where
    enforce is a custom function, default is the default value for this attribute, and
    required is a boolean.
    """
    if isinstance(schema, dict):
        enforce = schema['enforce'] if 'enforce' in schema else None
        default = schema['default'] if 'default' in schema else None
        required = schema['required'] if 'required' in schema else False
        return enforce, default, required
    return schema, None, None
