code: private String setCrsIds(String json, CrsId crsId) throws IOException, JsonException {
  
          /* Prepare a geojson crs structure
          "crs": {
              "type": "name",
                      "properties": {
                  "name": "EPSG:xxxx"
              }
          }
          */
          HashMap<String, Object> properties = new HashMap<String, Object>();
          properties.put("name", crsId.getAuthority() + ":" + crsId.getCode());
          HashMap<String, Object> type = new HashMap<String, Object>();
          type.put("type", "name");
          type.put("properties", properties);
  
          List<HashMap> result = parent.collectionFromJson(json, HashMap.class);
          
          for (HashMap geometryJson : result) {
              geometryJson.put("crs", type);
          }
  
          return parent.toJson(result);
      }
docs: Adds the given crs to all json objects. Used in {@link #asGeomCollection(org.geolatte.geom.crs.CrsId)}.
  
  @param json  the json string representing an array of geometry objects without crs property.
  @param crsId the crsId
  @return the same json string with the crs property filled in for each of the geometries.