presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/GeoFunctions.java/GeometryCollectionIterator/hasNext
class GeometryCollectionIterator:        @Override
        public boolean hasNext()
        {
            if (geometriesDeque.isEmpty()) {
                return false;
            }
            while (geometriesDeque.peek() instanceof OGCConcreteGeometryCollection) {
                OGCGeometryCollection collection = (OGCGeometryCollection) geometriesDeque.pop();
                for (int i = 0; i < collection.numGeometries(); i++) {
                    geometriesDeque.push(collection.geometryN(i));
                }
            }
            return !geometriesDeque.isEmpty();
        }