class_docstr: Create output filenames that work nicely with multiple input files from
  multiple directories (processing multiple subjects with one command)
  
  Use information from input files, out_dir and out_fnames to generate
  correct outputs which can come from long lists of multiple or single
  inputs.
code: def __init__(self, output_strategy="absolute", mix_names=False):
      self.output_strategy = output_strategy
      self.mix_names = mix_names
      self.inputs = []
      self.out_keys = None
  
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 1 to create a new IOIterator object  with example: obj = IOIterator(output_strategy, mix_names)