code: def __init__(self, loss_fcn, gamma=1.5, alpha=0.25):
      super(FocalLoss, self).__init__()
      self.loss_fcn = loss_fcn  # must be nn.BCEWithLogitsLoss()
      self.gamma = gamma
      self.alpha = alpha
      self.reduction = loss_fcn.reduction
      self.loss_fcn.reduction = "none"
  
imports: import glob
  import math
  import os
  import random
  import time
  import cv2
  import matplotlib
  import numpy
  import torch
  import torch.nn
  import torchvision
  from tqdm import tqdm
  from build_utils import torch_utils
label_desc: Use image node_id 1 to create a new FocalLoss object from inherited base classes: nn with example: obj = FocalLoss(loss_fcn, gamma, alpha)