class_docstr: Base data structure of SingleData and MultiData.
  
  NOTE:
  - For performance issue, only **np.floating** is supported in the underlayer data !!!
  - Boolean based on np.floating is also supported. Here are some examples
  
  .. code-block:: python
  
      np.array([ np.nan]).any() -> True
      np.array([ np.nan]).all() -> True
      np.array([1. , 0.]).any() -> True
      np.array([1. , 0.]).all() -> False
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code: def count(self):
      return len(self.data[~np.isnan(self.data)])
  
imports: from __future__ import annotations
  from typing import Dict, Tuple, Union, Callable, List
  import bisect
  import numpy
  import pandas
label_desc: Use image node_id 18 for calling the IndexData obj's underlying member method code with example usage: obj.count() and returns: len