Coerces string into separate string tags

voluptuous_tags.py

class Tags(object):
    """Converts string to tags, a list of string that was separated by comma

    """
    def __call__(self, v):
        if not isinstance(v, basestring) or v is None:
            raise Exception()
        tags = map(lambda x: x.strip(), list(v.split(',')))
        tags = filter(lambda x: x != '', tags)
        return tags

    def __repr__(self):
        return 'Tags()'