code: def focal_loss(y_true, y_pred, gamma=2):
      from keras import backend as K
  
      y_pred /= K.sum(y_pred, axis=-1, keepdims=True)
      eps = K.epsilon()
      y_pred = K.clip(y_pred, eps, 1.0 - eps)
      return -K.sum(
          K.pow(1.0 - y_pred, gamma) * y_true * K.log(y_pred), axis=-1
      )
  
imports: import numpy
  import itertools
label_desc: Use image node_id 7 for calling a global function with example usage: focal_loss(y_true, y_pred, gamma) and returns: unknown