docs: def _init_nodes(self, config):
          """ Gathers dependency sets onto _nodes """
          if not isinstance(config, dict):
              raise TypeError('"config" must be a dictionary')
  
          for (name, conf) in six.iteritems(config):
              args = [] if 'args' not in conf else conf['args']
              kwargs = {} if 'kwargs' not in conf else conf['kwargs']
  
              dependencies = set()
              arg_deps = self._get_dependencies_from_args(args)
              kwarg_deps = self._get_dependencies_from_kwargs(kwargs)
  
              dependencies.update(arg_deps)
              dependencies.update(kwarg_deps)
  
              self._nodes[name] = dependencies