code: def test_hash_extras():
      st = RamStorage()
      hw = HashWriter(st.create_file("test.hsh"))
      hw.extras["test"] = 100
      hw.add(b("foo"), b("bar"))
      hw.add(b("glonk"), b("baz"))
      hw.close()
  
      hr = HashReader.open(st, "test.hsh")
      assert hr.extras["test"] == 100
      assert hr.get(b("foo")) == b("bar")
      assert hr.get(b("baz")) is None
      hr.close()
  
file_path: whoosh/tests/test_tables.py
imports: from __future__ import with_statement
  import random
  from whoosh.compat import b, xrange, iteritems
  from whoosh.filedb.filestore import RamStorage
  from whoosh.filedb.filetables import HashReader, HashWriter
  from whoosh.filedb.filetables import OrderedHashWriter, OrderedHashReader
  from whoosh.util.testing import TempStorage
label_desc: Use image node_id 3 for calling a global function with example usage: test_hash_extras() without return types