code: def mpjpe_focal(pred, gt, has_3d_joints):
      """
      mPJPE loss
      """
      pred, gt = filter_3d_joints(pred, gt, has_3d_joints)
      mse_error = ((pred - gt) ** 2).sum(axis=-1)
      mpjpe_error = paddle.sqrt(mse_error)
      mean = mpjpe_error.mean()
      std = mpjpe_error.std()
      atte = 2 * F.sigmoid(6 * (mpjpe_error - mean) / std)
      mse_error *= atte
      return mse_error.mean()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from itertools import cycle, islice
  from collections import abc
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from ppdet.core.workspace import register, serializable
  from ppdet.utils.logger import setup_logger
label_desc: Use image node_id 3 for calling a global function with example usage: mpjpe_focal(pred, gt, has_3d_joints) and returns: mse_error