'Session will be saved to database with proper Event id
:param session_id:
:param user:
:param request: view data form
:param event_id: Session belongs to Event by event id'

@staticmethod
def add_speaker_to_session(request, event_id, session_id, user=login.current_user):

    session = DataGetter.get_session(session_id)
    speaker = save_speaker(request, event_id, user=user)
    session.speakers.append(speaker)
    sessions_modified.send(current_app._get_current_object(), event_id=session.event_id)
    save_to_db(session, 'Session    updated')
    update_version(event_id, False, 'speakers_ver')
    update_version(event_id, False, 'sessions_ver')
