Add representation methods to StorageMongoDb (#104)

* add representation methods to StorageMongoDb

src/qilib/utils/storage/mongo.py

@@ -93,6 +93,12 @@ def __init__(self, name: str, host: str = 'localhost', port: int = 27017, databa
         self._serialize = serializer.encode_data
         self._unserialize = serializer.decode_data
 
+    def __repr__(self) -> str:
+        return f'<{self.__class__.__name__} at 0x{id(self):x}: name {self._db.name}>'
+
+    def __str__(self) -> str:
+        return f'<{type(self).__name__}: name {self._db.name}>'
+
     def _check_server_connection(self, timeout: float) -> None:
         """ Check if connection has been established to database server."""
         try:

src/tests/unittests/utils/storage/test_storage_mongo.py

@@ -50,6 +50,14 @@ def tearDown(self) -> None:
         self.storage._collection.drop()
         self.dummy_storage._collection.drop()
 
+    def test_repr(self):
+        s=str(self.storage)
+        self.assertTrue(s.startswith('<StorageMongoDb'))
+        self.assertIn(self.storage.name, s)
+        s=repr(self.storage)
+        self.assertIn(f'{id(self.storage):x}', s)
+        self.assertIn(self.storage.name, s)
+
     def test_server_timeout(self):
         error_msg = 'Failed to connect to Mongo database within 0.01 milliseconds$'
         self.assertRaisesRegex(ConnectionTimeoutError, error_msg, StorageMongoDb, 'test', port=-1,