new_contents: import mr_streams as ms
  import unittest
  
  # :::: auxilary functions ::::
  def add_one(x):
      return x + 1
  
  def triplicate(x):
      return (x,x,x)
  
  def no_op(*args, **kwargs):
      pass
  
  class TestChaining(unittest.TestCase):
  
      def test_MaFiTaFlTkTpDr(self):
          _ = ms.stream(range(20))
  
          _.map(add_one)\
              .filter(lambda x: x%2 == 0)\
              .take(3)\
              .flatmap(triplicate)\
              .take(8)\
              .tap(no_op)
  
          _.drain()
subject: Fix bug in reduce and tap.