code: def test_existence_postings():
      content = u("alfa bravo charlie")
      assert _roundtrip(content, Existence(), "frequency") == [
          ("alfa", 1),
          ("bravo", 1),
          ("charlie", 1),
      ]
  
file_path: whoosh/tests/test_postings.py
imports: from __future__ import with_statement
  from whoosh import analysis, fields
  from whoosh.compat import u
  from whoosh.codec import default_codec
  from whoosh.formats import Existence, Frequency
  from whoosh.formats import Positions, PositionBoosts
  from whoosh.formats import Characters, CharacterBoosts
  from whoosh.util.testing import TempStorage
label_desc: Use image node_id 2 for calling a global function with example usage: test_existence_postings() without return types