code: def test_len(any_string_dtype):
      ser = Series(
          ["foo", "fooo", "fooooo", np.nan, "fooooooo", "foo\n", "あ"],
          dtype=any_string_dtype,
      )
      result = ser.str.len()
      expected_dtype = (
          "float64"
          if any_string_dtype in object_pyarrow_numpy
          else "Int64"
      )
      expected = Series(
          [3, 4, 6, np.nan, 8, 4, 1], dtype=expected_dtype
      )
      tm.assert_series_equal(result, expected)
  
imports: from datetime import datetime, timedelta
  import numpy
  import pytest
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
  from pandas.core.strings.accessor import StringMethods
  from pandas.tests.strings import object_pyarrow_numpy
label_desc: Use image node_id 14 for calling a global function with example usage: test_len(any_string_dtype) without return types