class_docstr: GrepDialog.__init__ calls parent SearchDiabolBase which attaches the
  passed in SearchEngine instance as attribute 'engine'. Only a few of the
  many possible self.engine.x attributes are needed here.
code: def getpat(self):
      return self._pat
  
imports: from idlelib import grep
  import unittest
  from test.support import captured_stdout
  from idlelib.idle_test.mock_tk import Var
  import os
  import re
label_desc: Use image node_id 1 for calling the Dummy_searchengine obj's underlying member method code with example usage: obj.getpat() and returns: self