code: def feature(self, instrument, field, start_index, end_index, freq):
      field = str(field)[1:]
      with pymongo.MongoClient(self.uri) as client:
          # TODO: this will result in frequently connecting the server and performance issue
          arctic = Arctic(client)
  
          if freq not in arctic.list_libraries():
              raise ValueError("lib {} not in arctic".format(freq))
  
          if instrument not in arctic[freq].list_symbols():
              # instruments does not exist
              return pd.Series()
          else:
              df = arctic[freq].read(
                  instrument,
                  columns=[field],
                  chunk_range=(start_index, end_index),
              )
              s = df[field]
  
              if not s.empty:
                  s = pd.concat(
                      [
                          s.between_time(time_tuple[0], time_tuple[1])
                          for time_tuple in self.market_transaction_time_list
                      ]
                  )
              return s
  
file_path: qlib/qlib/contrib/data/data.py
imports: from arctic import Arctic
  import pandas
  import pymongo
  from qlib.data.data import FeatureProvider
label_desc: Use image node_id 2 for calling the ArcticFeatureProvider obj's underlying member method code with example usage: obj.feature(instrument, field, start_index, end_index, freq) and returns: pd, s