Evaluate predictions with nerval

Based on !340 (merged)

Closes #231 (closed)

dan/ocr/manager/metrics.py

 # -*- coding: utf-8 -*-
 import re
 from collections import defaultdict
-from dataclasses import dataclass
 from operator import attrgetter
 from pathlib import Path
-from typing import Dict, List
+from typing import Dict, List, NamedTuple
 
 import editdistance
 import numpy as np
@@ -24,8 +23,7 @@ REGEX_ONLY_ONE_SPACE = re.compile(r"\s+")
 METRICS_KEYWORD = {"cer": "chars", "wer": "words", "ner": "tokens"}
 
 
-@dataclass
-class Inference:
+class Inference(NamedTuple):
     ground_truth: str
     prediction: str