def __init__(self, utm_source=None):
self._utm_source = None<EOL>if utm_source is not None:<EOL><INDENT>self.utm_source = utm_source<EOL><DEDENT>
Create a UtmSource object

        :param utm_source: Name of the referrer source.
            (e.g. Google, SomeDomain.com, or Marketing Email)
        :type utm_source: string, optional