code: def read(self, nodes=None, **kwargs):
          
          if nodes is None:
              required_nodes = self.wishlist - set(self.datasets.keys())
              nodes = self.dep_tree.leaves(nodes=required_nodes)
          return self._read_datasets(nodes, **kwargs)
docs: Load datasets from the necessary reader.
  
          Args:
              nodes (iterable): DependencyTree Node objects
              **kwargs: Keyword arguments to pass to the reader's `load` method.
  
          Returns:
              DatasetDict of loaded datasets