code: def __call__(self, expr, **kwargs):
      return _ExprRef(expr, **kwargs)
  
file_path: altair/altair/expr/__init__.py
imports: from typing import Any
  from .core import datum, Expression
  from .funcs import *
  from .consts import *
  from ..vegalite.v5.schema.core import ExprRef
label_desc: Use image node_id 2 for calling the _ExprType obj's underlying member method code with example usage: obj.__call__(expr) and returns: _ExprRef