code: def _make_msg(self, source="Subject: test\n\n", policy=None):
      self.policy = (
          email.policy.default.clone() if policy is None else policy
      )
      return email.message_from_string(source, policy=self.policy)
  
imports: import io
  import types
  import textwrap
  import unittest
  import email.errors
  import email.policy
  import email.parser
  import email.generator
  import email.message
  from email import headerregistry
label_desc: Use image node_id 7 for calling the TestPolicyPropagation obj's underlying member method code with example usage: obj._make_msg(source, policy) and returns: email