def __init__(<EOL>self, enable=None, text=None, html=None, substitution_tag=None):
self._enable = None<EOL>self._text = None<EOL>self._html = None<EOL>self._substitution_tag = None<EOL>if enable is not None:<EOL><INDENT>self.enable = enable<EOL><DEDENT>if text is not None:<EOL><INDENT>self.text = text<EOL><DEDENT>if html is not None:<EOL><INDENT>self.html = html<EOL><DEDENT>if substitution_tag is not None:<EOL><INDENT>self.substitution_tag = substitution_tag<EOL><DEDENT>
Create a SubscriptionTracking to customize subscription management.

        :param enable: Whether this setting is enabled.
        :type enable: boolean, optional
        :param text: Text to be appended to the email with the link as "<% %>".
        :type text: string, optional
        :param html: HTML to be appended to the email with the link as "<% %>".
        :type html: string, optional
        :param substitution_tag: Tag replaced with URL. Overrides text, html
                                 params.
        :type substitution_tag: string, optional