code: def _calc_fnr(tp: float, fp: float, fn: float) -> float:
      """Calculate FNR for given matches and number of positives."""
      if tp + fn == 0:
          return -1
      if tp + fp == 0:
          return 1
      return fn / (tp + fn + np.finfo(float).eps)
  
imports: import numpy
label_desc: Use image node_id 5 for calling a global function with example usage: _calc_fnr(tp, fp, fn) and returns: unknown, unknown, int