code: def _gain(p0, p1, n0, n1):
      """
      Calculation of p-foil gain for IREP*
  
      Parameters
      ----------
      p0 : int64
          Total positive instances
      p1 : int64
          Positive instances in the next iteration
      n0 : int64
          Total negative instances
      n1 : int64
          Negative instances in the next iteration
  
      Returns
      -------
      double
          The p-foil gian
      """
      if p1 == 0:
          return 0
      else:
          return p1 * (
              np.log2(p1 / (p1 + float(n1)))
              - np.log2(p0 / (p0 + float(n0)))
          )
  
imports: import numpy
  import numba
label_desc: Use image node_id 2 for calling a global function with example usage: _gain(p0, p1, n0, n1) and returns: int, unknown