code: def PRE_calc(P, POP):
      """
      Calculate Prevalence.
  
      :param P: number of actual positives
      :type P: int
      :param POP: population or total number of samples
      :type POP: int
      :return: prevalence as float
      """
      try:
          result = P / POP
          return result
      except (ZeroDivisionError, TypeError):
          return "None"
  
imports: from __future__ import division
  import math
  from .pycm_util import normal_quantile
  from .pycm_interpret import *
  from .pycm_param import CLASS_PARAMS
label_desc: Use image node_id 17 for calling a global function with example usage: PRE_calc(P, POP) and returns: result, str