refactor: simplify token2idx creation with dict comprehension (#168)

Signed-off-by: ktro2828 <kotaro.uetake@tier4.jp>

Author: ktro2828

t4_devkit/tier4.py

@@ -238,13 +238,12 @@ def __make_reverse_index__(self, verbose: bool) -> None:
         if verbose:
             print("Reverse indexing...")
 
-        token2idx: dict[str, dict[str, int]] = {}
-        for schema in SchemaName:
-            token2idx[schema.value] = {}
-            for idx, table in enumerate(self.get_table(schema.value)):
-                table: SchemaTable
-                token2idx[schema.value][table.token] = idx
-        self._token2idx = token2idx
+        self._token2idx: dict[str, dict[str, int]] = {
+            schema.value: {
+                table.token: idx for idx, table in enumerate(self.get_table(schema.value))
+            }
+            for schema in SchemaName
+        }
 
         self._label2id: dict[str, int] = {
             category.name: idx for idx, category in enumerate(self.category)