code: def testSetValue(self):
      self._tree.set(node_index=0, value=1.0)
      self.assertEqual(self._tree.get(0), 1.0)
  
      # Validate that all nodes on the leftmost branch have value 1.
      for level in self._tree.nodes:
          self.assertEqual(level[0], 1.0)
          nodes_at_this_depth = len(level)
          for i in range(1, nodes_at_this_depth):
              self.assertEqual(level[i], 0.0)
  
imports: import random
  import unittest
  from reagent.replay_memory import sum_tree
label_desc: Use image node_id 6 for calling the SumTreeTest obj's underlying member method code with example usage: obj.testSetValue() without return types