code: def test_subclassed_count(self):
      df = tm.SubclassedDataFrame(
          {
              "Person": ["John", "Myla", "Lewis", "John", "Myla"],
              "Age": [24.0, np.nan, 21.0, 33, 26],
              "Single": [False, True, True, True, False],
          }
      )
      result = df.count()
      assert isinstance(result, tm.SubclassedSeries)
  
      df = tm.SubclassedDataFrame(
          {"A": [1, 0, 3], "B": [0, 5, 6], "C": [7, 8, 0]}
      )
      result = df.count()
      assert isinstance(result, tm.SubclassedSeries)
  
      df = tm.SubclassedDataFrame(
          [
              [10, 11, 12, 13],
              [20, 21, 22, 23],
              [30, 31, 32, 33],
              [40, 41, 42, 43],
          ],
          index=MultiIndex.from_tuples(
              list(zip(list("AABB"), list("cdcd"))),
              names=["aaa", "ccc"],
          ),
          columns=MultiIndex.from_tuples(
              list(zip(list("WWXX"), list("yzyz"))),
              names=["www", "yyy"],
          ),
      )
      result = df.count()
      assert isinstance(result, tm.SubclassedSeries)
  
      df = tm.SubclassedDataFrame()
      result = df.count()
      assert isinstance(result, tm.SubclassedSeries)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 19 for calling the TestDataFrameSubclassing obj's underlying member method code with example usage: obj.test_subclassed_count() without return types