class_docstr: (D)ata(L)oader (W)ith (P)arser for features and names
  
  Extracting this class so that QlibDataLoader and other dataloaders(such as QdbDataLoader) can share the fields.
class_docstr_tok: ["(","D",")","ata","(","L",")","oader","(","W",")","ith","(","P",")","arser","for","features","and","names","Extracting","this","class","so","that","QlibDataLoader","and","other","dataloaders","(","such","as","QdbDataLoader",")","can","share","the","fields","."]
code: def load(
      self, instruments=None, start_time=None, end_time=None
  ) -> pd.DataFrame:
      if self.is_group:
          df = pd.concat(
              {
                  grp: self.load_group_df(
                      instruments,
                      exprs,
                      names,
                      start_time,
                      end_time,
                      grp,
                  )
                  for grp, (exprs, names) in self.fields.items()
              },
              axis=1,
          )
      else:
          exprs, names = self.fields
          df = self.load_group_df(
              instruments, exprs, names, start_time, end_time
          )
      return df
  
imports: import abc
  import pickle
  from pathlib import Path
  import warnings
  import pandas
  from typing import Tuple, Union, List
  from qlib.data import D
  from qlib.utils import load_dataset, init_instance_by_config, time_to_slc_point
  from qlib.log import get_module_logger
  from qlib.utils.serial import Serializable
label_desc: Use image node_id 4 for calling the DLWParser obj's underlying member method code with example usage: obj.load(instruments, start_time, end_time) and returns: df