code: def __getitem__(self, idx):
      if isinstance(idx, int):
          return self.values[idx + self.size]
      elif isinstance(idx, list):
          return self.values[np.array(idx) + self.size]
      else:
          raise RuntimeError("Not indexable type")
  
file_path: dynet/examples/reinforcement-learning/reduce_tree.py
imports: import operator
  import numpy
label_desc: Use image node_id 4 for calling the ReduceTree obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self, self