diff --git a/bit_manipulation/binary_and_operator.py b/bit_manipulation/binary_and_operator.py
index e5dffe3e31d2..f1b910f8cc9b 100644
--- a/bit_manipulation/binary_and_operator.py
+++ b/bit_manipulation/binary_and_operator.py
@@ -1,5 +1,6 @@
 # https://www.tutorialspoint.com/python3/bitwise_operators_example.htm
 
+
 def binary_and(a: int, b: int):
     """
     Take in 2 integers, convert them to binary,
diff --git a/bit_manipulation/binary_xor_operator.py b/bit_manipulation/binary_xor_operator.py
index 32a8f272116e..0edf2ba6606d 100644
--- a/bit_manipulation/binary_xor_operator.py
+++ b/bit_manipulation/binary_xor_operator.py
@@ -1,5 +1,6 @@
 # https://www.tutorialspoint.com/python3/bitwise_operators_example.htm
 
+
 def binary_xor(a: int, b: int):
     """
     Take in 2 integers, convert them to binary,
diff --git a/strings/remove_duplicate.py b/strings/remove_duplicate.py
index 6357050ac17d..5ab0e9962752 100644
--- a/strings/remove_duplicate.py
+++ b/strings/remove_duplicate.py
@@ -1,14 +1,15 @@
-""" Created by sarathkaul on 14/11/19 """
-
-
 def remove_duplicates(sentence: str) -> str:
     """
-    Reomove duplicates from sentence
+    Remove duplicates from sentence
     >>> remove_duplicates("Python is great and Java is also great")
     'Java Python also and great is'
+    >>> remove_duplicates("Python   is      great and Java is also great")
+    'Java Python also and great is'
     """
-    return " ".join(sorted(set(sentence.split(" "))))
+    return " ".join(sorted(set(sentence.split())))
 
 
 if __name__ == "__main__":
-    print(remove_duplicates("INPUT_SENTENCE"))
+    import doctest
+
+    doctest.testmod()