'Remove the last vol from an sg not associated with an mv.
Helper function for removing the last vol from a storage group
which is not associated with a masking view.
:param serial_number: the array serial number
:param storagegroup_name: the storage group name
:param device_id: the device id
:param volume_name: the volume name
:param extra_specs: the extra specifications
:param move: flag to indicate a move instead of remove
:returns: status -- bool'

def _last_vol_no_masking_views(self, serial_number, storagegroup_name, device_id, volume_name, extra_specs, move):

    parent_sg = self.get_parent_sg_from_child(serial_number, storagegroup_name)
    if (parent_sg is None):
        if move:
            self.add_volume_to_default_storage_group(serial_number, device_id, volume_name, extra_specs, src_sg=storagegroup_name)
        self.rest.delete_storage_group(serial_number, storagegroup_name)
        status = True
    else:
        num_vols_parent = self.rest.get_num_vols_in_sg(serial_number, parent_sg)
        if (num_vols_parent == 1):
            self._delete_cascaded_storage_groups(serial_number, storagegroup_name, parent_sg, extra_specs, device_id, move)
        else:
            self._remove_last_vol_and_delete_sg(serial_number, device_id, volume_name, storagegroup_name, extra_specs, parent_sg, move)
        status = True
    return status
