class_docstr: A dataset wrapping over a RecordIO (.rec) file.
  
  Each sample is a string representing the raw content of an record.
  
  Parameters
  ----------
  filename : str
      Path to rec file.
code: def __getitem__(self, idx):
      return self._record.read_idx(self._record.keys[idx])
  
imports: import os
  from ...None import recordio, ndarray
  from ...util import default_array
label_desc: Use image node_id 2 for calling the RecordFileDataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self