code: def visit_Expr(self, expr):
      if isinstance(expr.value, Name) and expr.value.id in self.mapping:
          if self.mapping[expr.value.id] is not None:
              return copy.deepcopy(self.mapping[expr.value.id])
      return self.generic_visit(expr)
  
file_path: catboost/contrib/python/ipython/py3/IPython/core/magics/ast_mod.py
imports: from ast import NodeTransformer, Store, Load, Name, Expr, Assign, Module
  import ast
  import copy
  from typing import Dict, Optional
label_desc: Use image node_id 4 for calling the ReplaceCodeTransformer obj's underlying member method code with example usage: obj.visit_Expr(expr) and returns: self, copy