code: def build_loss_fn(
      opts: argparse.Namespace,
      category: Optional[str] = "",
      *args,
      **kwargs,
  ) -> BaseCriteria:
      """Helper function to build loss function from command-line arguments.
  
      Args:
          opts: command-line arguments
          category: Optional task category (e.g., classification). Specifying category may be useful for
              building composite loss functions. See `loss_fns.composite_loss.CompositeLoss.build_composite_loss_fn`
              function for an example
  
      Returns:
          Loss function module
      """
  
      if not category:
          # If category is not specified, then read it from command-line arguments
          category = getattr(opts, "loss.category")
  
      if category is None:
          logger.error(
              "Please specify loss name using --loss.category. For composite loss function, see configuration"
              "example in `loss_fns.composite_loss.CompositeLoss`. Got None"
          )
  
      # Get the name of loss function for a given category.
      # Note that loss functions (e.g., NeuralAugmentation) that are not task-specific does not have this
      # argument defined. In such case, we set the loss function name the same as category
      if hasattr(opts, f"loss.{category}.name"):
          loss_fn_name = getattr(opts, f"loss.{category}.name")
      else:
          loss_fn_name = category
  
      # We registered the base criterion classes for different categories using a special `name` (i.e., `__base__`)
      # in order to access the arguments defined inside those classes. However, these classes are not supposed to
      # be used as a loss function. Therefore, we raise an error for such cases
      if loss_fn_name == "__base__":
          logger.error(
              "__base__ can't be used as a loss function name. Please check."
          )
  
      loss_fn = LOSS_REGISTRY[loss_fn_name, category](
          opts, *args, **kwargs
      )
      return loss_fn
  
imports: import argparse
  from typing import Optional
  from loss_fn.base_criteria import BaseCriteria
  from utils import logger
  from utils.registry import Registry
label_desc: Use image node_id 1 for calling a global function with example usage: build_loss_fn(opts, category) and returns: loss_fn