class_docstr: Convert msg spec V4 to V5
class_docstr_tok: ["Convert","msg","spec","V4","to","V5"]
code: def execute_reply(self, msg):
      content = msg["content"]
      user_expressions = content.setdefault("user_expressions", {})
      user_variables = content.pop("user_variables", {})
      if user_variables:
          user_expressions.update(user_variables)
  
      # Pager payloads became a mime bundle
      for payload in content.get("payload", []):
          if payload.get("source", None) == "page" and (
              "text" in payload
          ):
              if "data" not in payload:
                  payload["data"] = {}
              payload["data"]["text/plain"] = payload.pop("text")
  
      return msg
  
imports: import re
  import json
  from jupyter_client import protocol_version_info
label_desc: Use image node_id 4 for calling the V4toV5 obj's underlying member method code with example usage: obj.execute_reply(msg) and returns: msg