class_docstr: 评估parser的性能
class_docstr_tok: ["\u8bc4\u4f30parser\u7684\u6027\u80fd"]
code: def __init__(self):
      super().__init__()
      self.num_arc = 0
      self.num_label = 0
      self.num_sample = 0
  
file_path: fastNLP/tests/models/torch/test_biaffine_parser.py
imports: import pytest
  from fastNLP.envs.imports import _NEED_IMPORT_TORCH
  from fastNLP import Metric, seq_len_to_mask
  from .model_runner import *
label_desc: Use image node_id 1 to create a new ParserMetric object from inherited base classes: Metric with example: obj = ParserMetric()