@SuppressWarnings({"unchecked"})
public DataGridSamplePane() {
Column indexColumn = new Column("#", new RowNumberValueExtractor(), DataTypes.INT, "30px", null);
FieldColumn idColumn = new FieldColumn("ID", "id", DataTypes.INT, "50px", HasHorizontalAlignment.ALIGN_CENTER);
FieldColumn genderColumn = new FieldColumn("Gender", "gender", DataTypes.GENDER, "100px", HasHorizontalAlignment.ALIGN_CENTER);
genderColumn.setSortable(true);
genderColumn.setGroupable(true);
FieldColumn nameColumn = new FieldColumn("Name", "name", DataTypes.TEXT, "150px");
nameColumn.setSortable(true);
FieldColumn ageColumn = new FieldColumn("Age", "age", DataTypes.INT, null, HasHorizontalAlignment.ALIGN_CENTER);
ageColumn.setSortable(true);
ColumnSpec columns = new ColumnSpec()
.addColumn(indexColumn)
.addColumn(idColumn)
.addColumn(genderColumn)