code: def testAdd(self):
      db = descriptor_database.DescriptorDatabase()
      file_desc_proto = descriptor_pb2.FileDescriptorProto.FromString(
          factory_test2_pb2.DESCRIPTOR.serialized_pb
      )
      db.Add(file_desc_proto)
  
      self.assertEqual(
          file_desc_proto,
          db.FindFileByName(
              "google/protobuf/internal/factory_test2.proto"
          ),
      )
      self.assertEqual(
          file_desc_proto,
          db.FindFileContainingSymbol(
              "google.protobuf.python.internal.Factory2Message"
          ),
      )
      self.assertEqual(
          file_desc_proto,
          db.FindFileContainingSymbol(
              "google.protobuf.python.internal.Factory2Message.NestedFactory2Message"
          ),
      )
      self.assertEqual(
          file_desc_proto,
          db.FindFileContainingSymbol(
              "google.protobuf.python.internal.Factory2Enum"
          ),
      )
      self.assertEqual(
          file_desc_proto,
          db.FindFileContainingSymbol(
              "google.protobuf.python.internal.Factory2Message.NestedFactory2Enum"
          ),
      )
      self.assertEqual(
          file_desc_proto,
          db.FindFileContainingSymbol(
              "google.protobuf.python.internal.MessageWithNestedEnumOnly.NestedEnum"
          ),
      )
  
imports: from google.protobuf import descriptor_pb2
  from google.protobuf.internal import factory_test2_pb2
  from google.protobuf import descriptor_database
label_desc: Use image node_id 1 for calling the DescriptorDatabaseTest obj's underlying member method code with example usage: obj.testAdd() without return types