'Checks whether or not a user is already in a team in the given course.
Args:
user: the user that we want to query on
course_id: the course_id of the course we\'re interested in
Returns:
True if the user is on a team in the course already
False if not'

@classmethod
def user_in_team_for_course(cls, user, course_id):

    return cls.objects.filter(user=user, team__course_id=course_id).exists()
