class_docstr: A util class to collect test DataStream transformation results.
code: def clear(self):
      if self.j_data_stream_collect_sink is None:
          return
      self.j_data_stream_collect_sink.clear()
  
imports: import pickle
  from pyflink.datastream.functions import SinkFunction
  from pyflink.java_gateway import get_gateway
label_desc: Use image node_id 3 for calling the DataStreamTestSinkFunction obj's underlying member method code with example usage: obj.clear() without return types