The GeometryMultiLineString type represents a Geometry that is defined as the union of a set of GeometryLineString instances. GeometryMultiLineString is not equality comparable, so it cannot be used in keys. The meaning of a GeometryMultiLineString is as the meaning of MultiLineString in the OGC Simple Features specification ([OGC-SFACA/1.2.1] section 6.1.9).