code: def copy(src, trg, transform=None):
      ''' copy items with optional fields transformation
      '''
      source = open(src[0], src[1])
      target = open(trg[0], trg[1], autocommit=1000)
  
      for item in source.get():
          item = dict(item)
          if '_id' in item:
              del item['_id']
  
          if transform:
              item = transform(item)
          target.put(trg[0](item))
  
      source.close()
      target.commit()
      target.close(f copy(src, trg, transform=None):
      ''' copy items with optional fields transformation
      '''
      source = open(src[0], src[1])
      target = open(trg[0], trg[1], autocommit=1000)
  
      for item in source.get():
          item = dict(item)
          if '_id' in item:
              del item['_id']
  
          if transform:
              item = transform(item)
          target.put(trg[0](item))
  
      source.close()
      target.commit()
      target.close()
docs: copy items with optional fields transformation