code: async def open_async(self):
          
          self.set_pump_status("Opening")
          self.partition_context = PartitionContext(self.host, self.lease.partition_id,
                                                    self.host.eh_config.client_address,
                                                    self.host.eh_config.consumer_group,
                                                    self.loop)
          self.partition_context.lease = self.lease
          self.partition_context.event_processor_context = self.lease.event_processor_context
          self.processor = self.host.event_processor(self.host.event_processor_params)
          try:
              await self.processor.open_async(self.partition_context)
          except Exception as err:  # pylint: disable=broad-except
              # If the processor won't create or open, only thing we can do here is pass the buck.
              # Null it out so we don't try to operate on it further.
              await self.process_error_async(err)
              self.processor = None
              self.set_pump_status("OpenFailed")
  
          # If Open Async Didn't Fail call OnOpenAsync
          if self.pump_status == "Opening":
              await self.on_open_async()
docs: Opens partition pump.