class_docstr: MongoDB driver for image-match
  
      
docstr: Index a collection on words.
  
          
code: def index_collection(self):
      """Index a collection on words."""
      # Index on words
      self.index_names = [
          field
          for field in self.collection.find_one({}).keys()
          if field.find("simple") > -1
      ]
      for name in self.index_names:
          self.collection.create_index(name)
  
file_path: image-match/image_match/mongodb_driver.py
imports: from signature_database_base import SignatureDatabaseBase
  from signature_database_base import normalized_distance
  from multiprocessing import cpu_count, Process, Queue
  from multiprocessing.managers import Queue
  import numpy
label_desc: Use image node_id 4 for calling the SignatureMongo obj's underlying member method code with example usage: obj.index_collection() without return types