code: def slash_to_under(dir_str):
      return "".join(dir_str.replace("/", "_"))
  
imports: import inspect
  import itertools
  import numpy
  import os
  from glob import glob
  from dipy.workflows.base import get_args_default
label_desc: Use image node_id 2 for calling a global function with example usage: slash_to_under(dir_str) and returns: str