Docstring.

Author: Zvirovyi

src/core/state.py

@@ -189,12 +189,11 @@ def is_active(self) -> bool:
 
     @property
     def cassandra_password_secret(self) -> str:
-        """TODO."""
+        """Password of `cassandra` system user."""
         return self.relation_data.get("cassandra-password", "")
 
     @cassandra_password_secret.setter
     def cassandra_password_secret(self, value: str) -> None:
-        """TODO."""
         self._field_setter_wrapper("cassandra-password", value)