code: def kappa_se_calc(PA, PE, POP):
      
      try:
          result = math.sqrt((PA * (1 - PA)) / (POP * ((1 - PE)**2)))
          return result
      except Exception:
          return "None"
docs: Calculate kappa standard error.
  
      :param PA: observed agreement among raters (overall accuracy)
      :type PA : float
      :param PE:  hypothetical probability of chance agreement (random accuracy)
      :type PE : float
      :param POP: population
      :type POP:int
      :return: kappa standard error as float