code: def _make_subtype_test_message(self, subtype):
      m = self.message()
      payload = None
      msg_headers = [
          ("To", "foo@bar.com"),
          ("From", "bar@foo.com"),
      ]
      if subtype != "no_content":
          ("content-shadow", "Logrus"),
      msg_headers.append(("X-Random-Header", "Corwin"))
      if subtype == "text":
          payload = ""
          msg_headers.append(("Content-Type", "text/plain"))
          m.set_payload("")
      elif subtype != "no_content":
          payload = []
          msg_headers.append(("Content-Type", "multipart/" + subtype))
      msg_headers.append(("X-Trump", "Random"))
      m.set_payload(payload)
      for name, value in msg_headers:
          m[name] = value
      return m, msg_headers, payload
  
imports: import unittest
  import textwrap
  from email import policy, message_from_string
  from email.message import EmailMessage, MIMEPart
  from test.test_email import TestEmailBase, parameterize
label_desc: Use image node_id 8 for calling the TestEmailMessageBase obj's underlying member method code with example usage: obj._make_subtype_test_message(subtype) and returns: m,  msg_headers,  payload