docs: def setup_dump(self):
          """
          Set up dump, creating directories and writing step.yaml file
          containing yaml dump of this step.
  
          {drain.PATH}/{self._digest}/
              step.yaml
              dump/
          """
          dumpdir = self._dump_dirname
          if not os.path.isdir(dumpdir):
              os.makedirs(dumpdir)
  
          dump = False
          yaml_filename = self._yaml_filename
  
          if not os.path.isfile(yaml_filename):
              dump = True
          else:
              with open(yaml_filename) as f:
                  if f.read() != yaml.dump(self):
                      logging.warning('Existing step.yaml does not match hash, regenerating')
                      dump = True
  
          if dump:
              with open(yaml_filename, 'w') as f:
                  yaml.dump(self, f)