docs: def load(steps, reload=False):
      """
      safely load steps in place, excluding those that fail
      Args:
          steps: the steps to load
      """
      # work on collections by default for fewer isinstance() calls per call to load()
      if reload:
          _STEP_CACHE.clear()
  
      if callable(steps):
          steps = steps()
  
      if not isinstance(steps, collections.Iterable):
          return load([steps])[0]
  
      loaded = []
      for s in steps:
          digest = s._digest
          if digest in _STEP_CACHE:
              loaded.append(_STEP_CACHE[digest])
          else:
              try:
                  s.load()
                  _STEP_CACHE[digest] = s
                  loaded.append(s)
              except(Exception):
                  logging.warn('Error during step load:\n%s' %
                               util.indent(traceback.format_exc()))
  
      return loaded