code: def find_deprecated_usages(
      schema: GraphQLSchema, ast: DocumentNode
  ) -> List[GraphQLError]:
      
  
      type_info = TypeInfo(schema)
      visitor = FindDeprecatedUsages(type_info)
      visit(ast, TypeInfoVisitor(type_info, visitor))
      return visitor.errors
docs: Get a list of GraphQLError instances describing each deprecated use.