code: def test_context_meter_nested_floor():
      """Subtracting calls from nested context_meter.meter() calls can cause the outermost
      calls to drop below the floor
      """
      it1 = iter([123, 125])
      it2 = iter([124, 128])
      cbs = []
  
      with metrics.context_meter.add_callback(
          lambda l, v, u: cbs.append((l, v, u))
      ):
          with metrics.context_meter.meter(
              "m1", func=lambda: next(it1), floor=0.1
          ) as m1:
              with metrics.context_meter.meter(
                  "m2", func=lambda: next(it2)
              ):
                  pass
  
      assert m1.delta == 0.1
      assert cbs == [("m2", 4, "seconds"), ("m1", 0.1, "seconds")]
  
imports: from __future__ import annotations
  import math
  import pickle
  import threading
  import time
  import pytest
  from distributed import metrics
  from distributed.compatibility import WINDOWS
  from distributed.utils import offload
  from distributed.utils_test import gen_test
label_desc: Use image node_id 10 for calling a global function with example usage: test_context_meter_nested_floor() without return types