code: def l1_loss(pred, target):
      """L1 loss.
  
      Args:
          pred (torch.Tensor): The prediction.
          target (torch.Tensor): The learning target of the prediction.
  
      Returns:
          torch.Tensor: Calculated loss
      """
      assert pred.size() == target.size() and target.numel() > 0
      loss = torch.abs(pred - target)
      return loss
  
file_path: insightface/detection/scrfd/mmdet/models/losses/smooth_l1_loss.py
imports: import torch
  import torch.nn
  from ..builder import LOSSES
  from .utils import weighted_loss
label_desc: Use image node_id 2 for calling a global function with example usage: l1_loss(pred, target) and returns: loss