code: def undefined_var_message(var_name, op_name=None):
      if op_name:
          return (
              'Variable "${}" is not defined by operation "{}".'.format(
                  var_name, op_name
              )
          )
      return 'Variable "${}" is not defined.'.format(var_name)
  
file_path: wandb/wandb/vendor/graphql-core-1.1/wandb_graphql/validation/rules/no_undefined_variables.py
imports: from ...error import GraphQLError
  from .base import ValidationRule
label_desc: Use image node_id 2 for calling the NoUndefinedVariables obj's underlying member method code with example usage: obj.undefined_var_message(var_name, op_name) and returns: str, str