public SerializableFunction<T, Row> getToRowFunction() {
    return toRowFunction;
  }
@Test
  public void testNullMapProtoToRow() throws InvalidProtocolBufferException {
    ProtoDynamicMessageSchema schemaProvider = schemaFromDescriptor(MapPrimitive.getDescriptor());
    SerializableFunction<DynamicMessage, Row> toRow = schemaProvider.getToRowFunction();
    assertEquals(NULL_MAP_PRIMITIVE_ROW, toRow.apply(toDynamic(NULL_MAP_PRIMITIVE_PROTO)));
  }