code: public NumberExpression<Integer> numGeometries() {
          if (numGeometries == null) {
              numGeometries = Expressions.numberOperation(Integer.class, SpatialOps.NUM_GEOMETRIES, mixin);
          }
          return numGeometries;
      }
docs: Returns the number of geometries in this GeometryCollection.
  
  @return number of geometries