code: def __init__(self):
      super(MyMetric, self).__init__()
      self.register_element(name="t1", value=0)
      self.register_element(name="t2", value=0)
      self.register_element(name="t3", value=0)
  
file_path: fastNLP/tests/core/metrics/test_element_cal_element.py
imports: import pytest
  from fastNLP.core.metrics import Metric
  from fastNLP.envs.imports import _NEED_IMPORT_TORCH
  from .utils import find_free_network_port, setup_ddp
label_desc: Use image node_id 1 to create a new MyMetric object from inherited base classes: Metric with example: obj = MyMetric()