code: def _isna_compat(arr, fill_value=np.nan):
      
      dtype = arr.dtype
      if isna(fill_value):
          return not (is_bool_dtype(dtype) or
                      is_integer_dtype(dtype))
      return True
docs: Parameters
      ----------
      arr: a numpy array
      fill_value: fill value, default to np.nan
  
      Returns
      -------
      True if we can fill using this fill_value