code: def start_completion(self, buffer_name=None, select_first=False,
                           select_last=False, insert_common_part=False,
                           complete_event=None):
          
          buffer_name = buffer_name or self.current_buffer_name
          completer = self._async_completers.get(buffer_name)
  
          if completer:
              completer(select_first=select_first,
                        select_last=select_last,
                        insert_common_part=insert_common_part,
                        complete_event=CompleteEvent(completion_requested=True))
docs: Start asynchronous autocompletion of this buffer.
          (This will do nothing if a previous completion was still in progress.)