'Return size of snapshot to be managed by manage_existing.
We expect a snapshot name in the existing_ref that matches one in
Purity.'

def manage_existing_snapshot_get_size(self, snapshot, existing_ref):

    self._verify_manage_snap_api_requirements()
    snap_info = self._validate_manage_existing_ref(existing_ref, is_snap=True)
    size = self._round_bytes_to_gib(snap_info['size'])
    return size
