<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _send_invitation(self, enrollment, event):
 """Send an invitation mail to an open enrolment"""


        self.log('Sending enrollment status mail to user')

        self._send_mail(self.config.invitation_subject, self.config.invitation_mail, enrollment, event)