class_docstr: This class maintains a pandas.dataframe of filenames for all input sections.
  The list of filenames are obtained by searching the specified folders
  or loading from an existing csv file.
  
  Users can query a subset of the dataframe by train/valid/infer partition
  label and input section names.
docstr: reset all fields of this singleton class.
docstr_tok: ["reset","all","fields","of","this","singleton","class","."]
code: def reset(self):
      """
      reset all fields of this singleton class.
      """
      self._file_list = None
      self._partition_ids = None
      self.data_param = None
      self.ratios = None
      self.new_partition = False
  
      self.data_split_file = ""
      self.default_image_file_location = (
          NiftyNetGlobalConfig().get_niftynet_home_folder()
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import os
  import random
  import shutil
  import pandas
  import tensorflow
  from niftynet.engine.signal import TRAIN, VALID, INFER, ALL
  from niftynet.utilities.decorators import singleton
  from niftynet.utilities.filename_matching import KeywordsMatching
  from niftynet.utilities.niftynet_global_config import NiftyNetGlobalConfig
  from niftynet.utilities.util_common import look_up_operations
  from niftynet.utilities.util_csv import match_and_write_filenames_to_csv
  from niftynet.utilities.util_csv import write_csv
label_desc: Use image node_id 18 for calling the ImageSetsPartitioner obj's underlying member method code with example usage: obj.reset() without return types