docstr: Executes all queued preprocessor functions in this DataCollection.
          
docstr_tok: ["Executes","all","queued","preprocessor","functions","in","this","DataCollection","."]
code: def preprocess(self):
      """Executes all queued preprocessor functions in this DataCollection."""
  
      for idx, preprocessor in enumerate(self.preprocessors):
          preprocessor.reset()
          if idx == len(self.preprocessors) - 1:
              preprocessor.execute(self, return_array=True)
          else:
              preprocessor.execute(self, return_array=False)
  
imports: import os
  import csv
  import numpy
  import tables
  import copy
  from tqdm import tqdm
  from deepneuro.augmentation.augment import Copy
  from deepneuro.utilities.conversion import read_image_files
  from deepneuro.data.data_group import DataGroup
  from deepneuro.data.data_load import parse_directories, parse_filepaths, parse_hdf5, parse_csv, parse_numpy
  from deepneuro.utilities.util import add_parameter
label_desc: Use image node_id 13 for calling the DataCollection obj's underlying member method code with example usage: obj.preprocess() without return types