code: def _create_index():
      s = fields.Schema(
          f1=fields.KEYWORD(stored=True),
          f2=fields.KEYWORD,
          f3=fields.KEYWORD,
      )
      st = RamStorage()
      ix = st.create_index(s)
      return ix
  
imports: from __future__ import with_statement
  import random, threading, time
  import pytest
  from whoosh import fields, formats, reading
  from whoosh.compat import b, u, xrange
  from whoosh.reading import SegmentReader
  from whoosh.filedb.filestore import RamStorage
  from whoosh.util.testing import TempIndex
label_desc: Use image node_id 1 for calling a global function with example usage: _create_index() and returns: ix