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