Fix: added call to doctest in main files.

Author: Dajamante

data_structures/queue/circular_queue.py

@@ -92,3 +92,9 @@ def dequeue(self):
         self.front = (self.front + 1) % self.n
         self.size -= 1
         return temp
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()

data_structures/queue/linked_queue.py

@@ -149,6 +149,6 @@ def clear(self) -> None:
 
 
 if __name__ == "__main__":
-    from doctest import testmod
+    import doctest
 
-    testmod()
+    doctest.testmod()

data_structures/queue/queue_on_list.py

@@ -50,3 +50,9 @@ def get_front(self):
 
     def size(self):
         return self.length
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()