code: def test_is_attachment(self):
      m = self._make_message()
      self.assertFalse(m.is_attachment())
      m["Content-Disposition"] = "inline"
      self.assertFalse(m.is_attachment())
      m.replace_header("Content-Disposition", "attachment")
      self.assertTrue(m.is_attachment())
      m.replace_header("Content-Disposition", "AtTachMent")
      self.assertTrue(m.is_attachment())
      m.set_param("filename", "abc.png", "Content-Disposition")
      self.assertTrue(m.is_attachment())
  
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 18 for calling the TestEmailMessageBase obj's underlying member method code with example usage: obj.test_is_attachment() without return types