[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

maths/is_string_palindrome.py

@@ -38,9 +38,10 @@ def is_string_palindrome(words: str) -> bool:
     >>> is_string_palindrome(" ")
     True
     """
-    cleaned_phrase = ''.join(words.split()).lower()
+    cleaned_phrase = "".join(words.split()).lower()
     return cleaned_phrase == cleaned_phrase[::-1]
 
+
 if __name__ == "__main__":
     import doctest