code: def on_timer(self, timestamp):
      results = self._main_operation.on_timer(timestamp)
  
      if results:
          results = self._process_elements(results)
          yield from self._output_elements(results)
  
file_path: flink/flink-python/pyflink/fn_execution/embedded/operations.py
imports: from pyflink.fn_execution.datastream.embedded.operations import extract_process_function
  from pyflink.fn_execution.embedded.converters import DataConverter
label_desc: Use image node_id 4 for calling the FunctionOperation obj's underlying member method code with example usage: obj.on_timer(timestamp) without return types