[fix] set label_map in Detectron2LayoutModel (Layout-Parser#75)

* remove unused type annotations

* automatically set label_map in Detectron2LayoutModel

Author: lolipopshock

src/layoutparser/models/detectron2/layoutmodel.py

@@ -90,6 +90,13 @@ def __init__(
         )
         config_path = PathManager.get_local_path(config_path)
 
+        if label_map is None:
+            if config_path.startswith("lp://"):
+                dataset_name = config_path.lstrip("lp://").split("/")[1]
+                label_map = LABEL_MAP_CATALOG[dataset_name]
+            else:
+                label_map = {}
+
         cfg = detectron2.config.get_cfg()
         cfg.merge_from_file(config_path)
         cfg.merge_from_list(extra_config)
@@ -126,8 +133,8 @@ def gather_output(self, outputs):
         for score, box, label in zip(scores, boxes, labels):
             x_1, y_1, x_2, y_2 = box
 
-            if self.label_map is not None:
-                label = self.label_map.get(label, label)
+
+            label = self.label_map.get(label, label)
 
             cur_block = TextBlock(
                 Rectangle(x_1, y_1, x_2, y_2), type=label, score=score

src/layoutparser/models/model_config.py

@@ -32,7 +32,6 @@
     - Brief format: lp://<dataset-name>/<config, weight>
 """
 
-from typing import List, OrderedDict, Union, Dict, Any, Tuple, Optional, NamedTuple
 from dataclasses import dataclass
 
 LAYOUT_PARSER_MODEL_PREFIX = "lp://"