'Returns a boolean indicating whether an OperatorPermission object
exists for the passed user, carrier, and region.
Example:
has_permission = OperatorPermission.has_permission(
request.user, request.REGION.id, get_carrier_id())'

@classmethod
def has_permission(cls, user, carrier, region):

    return cls.objects.get(user=user, carrier=carrier, region=region).exists()
