{
  "name": "union",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Returns a geometry that represents the point set union of the geometries.",
  "arguments": [ {"arg":"geometry1","description":"a geometry"},
                 {"arg":"geometry2","description":"a geometry"}],
  "examples": [ { "expression":"geom_to_wkt( union( make_point(4, 4), make_point(5, 5) ) )", "returns":"'MULTIPOINT(4 4, 5 5)'"} ]
}