Return element or traceline IDs referenced by the supplied node IDs.
id=get_id_by_nid(fem)
id=get_id_by_nid(fem,nid)
id=get_id_by_nid(fem,nid,'elem')
GET_ID_BY_NID returns a sorted list of node IDs that make up the connectivity of the IDs supplied. If NID is not supplied, or is empty, all of the entities will be used.
TYPE is an optional string specifying the entity from which to extract the associated IDs. Valid options are 'elem' (default) and 'tl'.