code: def enter_OperationDefinition(self, node):
      definition_type = None
      if node.operation == "query":
          definition_type = self._schema.get_query_type()
      elif node.operation == "mutation":
          definition_type = self._schema.get_mutation_type()
  
      self._type_stack.append(definition_type)
  
imports: from ..language import visitor_meta
  from ..type.definition import GraphQLInputObjectType, GraphQLList, get_named_type, get_nullable_type, is_composite_type
  from .get_field_def import get_field_def
  from .type_from_ast import type_from_ast
label_desc: Use image node_id 13 for calling the TypeInfo obj's underlying member method code with example usage: obj.enter_OperationDefinition(node) without return types