code: def test_as_string_unixform(self):
      m = self._str_msg("test")
      m.set_unixfrom("From foo@bar Thu Jan  1 00:00:00 1970")
      self.assertEqual(
          m.as_string(unixfrom=True),
          "From foo@bar Thu Jan  1 00:00:00 1970\n\ntest",
      )
      self.assertEqual(m.as_string(unixfrom=False), "\ntest")
  
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 5 for calling the TestEmailMessage obj's underlying member method code with example usage: obj.test_as_string_unixform() without return types