text: import unittest
  
  import reactivex
  from reactivex import operators as ops
  
  
  class TestGroupByReduce(unittest.TestCase):
      def test_groupby_count(self):
          res = []
          counts = reactivex.from_(range(10)).pipe(
              ops.group_by(lambda i: "even" if i % 2 == 0 else "odd"),
              ops.flat_map(
                  lambda i: i.pipe(
                      ops.count(),
                      ops.map(lambda ii: (i.key, ii)),
                  )
              ),
          )
  
          counts.subscribe(on_next=res.append)
          assert res == [("even", 5), ("odd", 5)]
  
      def test_window_sum(self):
          res = []
          reactivex.from_(range(6)).pipe(
              ops.window_with_count(count=3, skip=1),
              ops.flat_map(
                  lambda i: i.pipe(
                      ops.sum(),
                  )
              ),
          ).subscribe(on_next=res.append)
  
          assert res == [3, 6, 9, 12, 9, 5, 0]
  