add ls, start and end command

lib/DataStore.py

@@ -9,7 +9,7 @@ class DataStore:
         if create:
             # Store emtpty list
             self._time_slots = []
-            self._write_update()
+            self.write_update()
         else:
             # Load dicts from file
             with open(self._filename, "r") as f:
@@ -23,18 +23,18 @@ class DataStore:
 
             self._time_slots = [deserialize(d) for d in self._time_slots]
 
-    def _write_update(self):
+    def write_update(self):
         """Saves the updates made to the DataStore object to disk."""
         with open(self._filename, "w+") as f:
             json.dump(self._time_slots, f, default=vars)
 
     def add_time_slot(self, time_slot: TimeSlot):
         self._time_slots.append(time_slot)
-        self._write_update()
+        self.write_update()
 
     def remove_time_slot(self, time_slot: TimeSlot):
         self._time_slots.remove(time_slot)
-        self._write_update()
+        self.write_update()
 
     def get_all_time_slots(self):
         return self._time_slots[:]