code: def testGetField(self):
      proto = sc_pb.ResponseObservation(
          observation=sc_pb.Observation(
              game_loop=1, alerts=[sc_pb.AlertError]
          )
      )
  
      game_loop = proto_diff.ProtoPath(("observation", "game_loop"))
      alert = proto_diff.ProtoPath(("observation", "alerts", 0))
      self.assertEqual(game_loop.get_field(proto), 1)
      self.assertEqual(alert.get_field(proto), sc_pb.AlertError)
      self.assertEqual(
          proto_diff.ProtoPath(game_loop.path[:-1]).get_field(proto),
          sc_pb.Observation(game_loop=1, alerts=[sc_pb.AlertError]),
      )
  
imports: from absl.testing import absltest
  from pysc2.lib import proto_diff
  from s2clientprotocol import sc2api_pb2
  from s2clientprotocol import score_pb2
label_desc: Use image node_id 9 for calling the ProtoPathTest obj's underlying member method code with example usage: obj.testGetField() without return types