class_docstr: NodeVisitor that builds a set of all of the named identifiers in an AST
class_docstr_tok: ["NodeVisitor","that","builds","a","set","of","all","of","the","named","identifiers","in","an","AST"]
code: def visit_arg(self, node):
      if hasattr(node, "arg"):
          self.names.add(node.arg)
      elif hasattr(node, "id"):
          self.names.add(node.id)
  
imports: import re
  import copy
  import inspect
  import ast
  import textwrap
label_desc: Use image node_id 3 for calling the NameVisitor obj's underlying member method code with example usage: obj.visit_arg(node) without return types