docstr: Returns result of applying `self.operation`
  to a contiguous subsequence of the array.
  Parameters
  ----------
  start: int
      beginning of the subsequence
  end: int
      end of the subsequences
  Returns
  -------
  reduced: obj
      result of reducing self.operation over the specified range of array.
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code: def reduce(self, start=0, end=None):
      """Returns result of applying `self.operation`
      to a contiguous subsequence of the array.
      Parameters
      ----------
      start: int
          beginning of the subsequence
      end: int
          end of the subsequences
      Returns
      -------
      reduced: obj
          result of reducing self.operation over the specified range of array.
      """
      if end is None:
          end = self._capacity
      if end < 0:
          end += self._capacity
      end -= 1
      return self._reduce_helper(start, end, 1, 0, self._capacity - 1)
  
imports: import argparse
  import operator
  import os
  import random
  import time
  import gym
  import matplotlib.pyplot
  import numpy
  import tensorflow
  import tensorlayer
label_desc: Use image node_id 3 for calling the SegmentTree obj's underlying member method code with example usage: obj.reduce(start, end) and returns: self