code: @SuppressWarnings("rawtypes")
      public static Point2D getOffset( Symbolizer symbolizer ) {
          Expression geometry = symbolizer.getGeometry();
          if (geometry != null) {
              if (geometry instanceof FilterFunction_offset) {
                  FilterFunction_offset offsetFunction = (FilterFunction_offset) geometry;
                  List parameters = offsetFunction.getParameters();
                  Expression xOffsetExpr = (Expression) parameters.get(1);
                  Expression yOffsetExpr = (Expression) parameters.get(2);
                  Double xOffsetDouble = xOffsetExpr.evaluate(null, Double.class);
                  Double yOffsetDouble = yOffsetExpr.evaluate(null, Double.class);
                  if (xOffsetDouble != null && yOffsetDouble != null) {
                      Point2D.Double point = new Point2D.Double(xOffsetDouble, yOffsetDouble);
                      return point;
                  }
              }
          }
          return null;
      }
docs: Get the offset from a {@link Symbolizer}.
  
  @param symbolizer the symbolizer.
  @return the offset.