Fix snapshot functionality by adjusting execution order

Author: Susmita-Chakrabarty

pydatastructs/graphs/graph.py

@@ -75,23 +75,12 @@ def __new__(cls, *args, **kwargs):
             cls, kwargs.get('backend', Backend.PYTHON))
         default_impl = args[0]._impl if args else 'adjacency_list'
         implementation = kwargs.get('implementation', default_impl)
-        if implementation == 'adjacency_list':
-            from pydatastructs.graphs.adjacency_list import AdjacencyList
-            obj = AdjacencyList(*args)
-            obj._impl = implementation
-            return obj
-        elif implementation == 'adjacency_matrix':
-            from pydatastructs.graphs.adjacency_matrix import AdjacencyMatrix
-            obj = AdjacencyMatrix(*args)
-            obj._impl = implementation
-            return obj
-        else:
-            raise NotImplementedError("%s implementation is not a part "
-                                      "of the library currently."%(implementation))
-        obj.snapshots = {}
+        obj._impl = implementation
+        obj.snapshots = {}  
+
         def add_snapshot(self):
             """Automatically assigns timestamps using system time."""
-            timestamp = int(time.time())  # Secure real-time timestamp
+            timestamp = int(time.time())
             self.snapshots[timestamp] = copy.deepcopy(self)
         def get_snapshot(self, timestamp: int):
             """Retrieves a past version of the graph if the timestamp exists."""
@@ -104,12 +93,26 @@ def list_snapshots(self):
             """Returns all stored timestamps in sorted order."""
             return sorted(self.snapshots.keys())
 
-        # Attach functions to the object
+       
         obj.add_snapshot = add_snapshot.__get__(obj)
         obj.get_snapshot = get_snapshot.__get__(obj)
         obj.list_snapshots = list_snapshots.__get__(obj)
 
-        return obj
+        
+        if implementation == 'adjacency_list':
+            from pydatastructs.graphs.adjacency_list import AdjacencyList
+            obj = AdjacencyList(*args)
+            obj._impl = implementation
+            return obj
+        elif implementation == 'adjacency_matrix':
+            from pydatastructs.graphs.adjacency_matrix import AdjacencyMatrix
+            obj = AdjacencyMatrix(*args)
+            obj._impl = implementation
+            return obj
+        else:
+            raise NotImplementedError("%s implementation is not a part "
+                                      "of the library currently."%(implementation))
+      
 
     def is_adjacent(self, node1, node2):
         """