code: def testNegativeCapacity(self):
      with self.assertRaises(
          ValueError,
          msg="Sum tree capacity should be positive. Got: -1",
      ):
          sum_tree.SumTree(capacity=-1)
  
imports: import random
  import unittest
  from reagent.replay_memory import sum_tree
label_desc: Use image node_id 2 for calling the SumTreeTest obj's underlying member method code with example usage: obj.testNegativeCapacity() without return types