api: names are locally caches

It improve speed because it avoid doing requests to the DB

src/numbat/api.py

@@ -59,6 +59,7 @@ def __init__(self, database: sqlite3.Connection, path: Path, logger: logging.Log
             self.logger = logging.getLogger()
         else:
             self.logger = logger
+        self.name_cache = dict()
 
     # ------------------------------------------------------------------------ #
     # Database file management functions                                       #
@@ -80,6 +81,19 @@ def __uniformize_path(cls, path: Path | str) -> Path:
             path = path.with_suffix(cls.SOURCETRAIL_DB_EXT)
         return path.absolute()
 
+    @classmethod
+    def exists(cls, path: Path | str) -> bool:
+        """
+        This method check if there is a Sourcetrail db with the given path.
+        If the provided path does not end with the sourcetrail db correct
+        suffix. It will be added.
+
+        :param path: The path to test
+        :return: a bool
+        """
+        path = cls.__uniformize_path(path)
+        return path.exists()
+
     @classmethod
     def open(cls, path: Path | str, clear: bool = False) -> 'SourcetrailDB':
         """
@@ -229,8 +243,7 @@ def __add_if_not_existing(self, name: str, type_: NodeType) -> int:
                  the existing one
         """
 
-        node = NodeDAO.get_by_name(self.database, name)
-        if not node:
+        if name not in self.name_cache:
             elem = Element()
             elem.id = ElementDAO.new(self.database, elem)
 
@@ -240,9 +253,10 @@ def __add_if_not_existing(self, name: str, type_: NodeType) -> int:
                 name
             ))
 
+            self.name_cache[name] = elem.id
             return elem.id
         else:
-            return node.id
+            return self.name_cache[name]
 
     def _record_symbol(self, hierarchy: NameHierarchy) -> int:
         """