code: def test_len(self, float_frame):
      assert len(float_frame) == len(float_frame.index)
  
      # single block corner case
      arr = float_frame[["A", "B"]].values
      expected = float_frame.reindex(columns=["A", "B"]).values
      tm.assert_almost_equal(arr, expected)
  
imports: from copy import deepcopy
  import inspect
  import pydoc
  import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas._config.config import option_context
  import pandas
  from pandas import DataFrame, Series, date_range, timedelta_range
  import pandas._testing
label_desc: Use image node_id 11 for calling the TestDataFrameMisc obj's underlying member method code with example usage: obj.test_len(float_frame) without return types