code: def __init__(self, size, op):
      if size & (size - 1) != 0:
          raise ValueError("size mush be a power of 2.")
      self.size = size
      self.values = np.zeros(2 * self.size)
      self.op = op
  
file_path: dynet/examples/reinforcement-learning/reduce_tree.py
imports: import operator
  import numpy
label_desc: Use image node_id 1 to create a new ReduceTree object from inherited base classes: object with example: obj = ReduceTree(size, op)