class_docstr: A Trigger that fires once the count of elements in a pane reaches the given count.
code: def on_merge(self, window: W, merge_context: TriggerContext):
      merge_context.merge_partitioned_state(self._count_state_desc)
  
imports: from abc import abstractmethod, ABC
  from typing import Generic
  from pyflink.common.typeinfo import Types
  from pyflink.datastream.state import ValueStateDescriptor
  from pyflink.datastream.window import TimeWindow, CountWindow
  from pyflink.fn_execution.table.window_context import TriggerContext, W
label_desc: Use image node_id 6 for calling the CountTrigger obj's underlying member method code with example usage: obj.on_merge(window, merge_context) without return types