code: def test_str_defaults_to_utf8(self):
      m = EmailMessage()
      m["Subject"] = "unicöde"
      self.assertEqual(str(m), "Subject: unicöde\n\n")
  
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 7 for calling the TestEmailMessage obj's underlying member method code with example usage: obj.test_str_defaults_to_utf8() without return types