Enhance palindrome functions with type validation

Refactor palindrome functions to include type checks and remove unnecessary comments.

Author: Kalyani-Puranik

strings/palindrome.py

@@ -19,12 +19,8 @@
 
 
 def is_palindrome(s: str) -> bool:
-    """
-    Return True if s is a palindrome otherwise return False.
-
-    >>> all(is_palindrome(key) is value for key, value in test_data.items())
-    True
-    """
+    if not isinstance(s, str):
+        return False
 
     start_i = 0
     end_i = len(s) - 1
@@ -38,23 +34,16 @@ def is_palindrome(s: str) -> bool:
 
 
 def is_palindrome_traversal(s: str) -> bool:
-    """
-    Return True if s is a palindrome otherwise return False.
+    if not isinstance(s, str):
+        return False
+    if len(s) < 2:
+        return True
 
-    >>> all(is_palindrome_traversal(key) is value for key, value in test_data.items())
-    True
-    """
     end = len(s) // 2
     n = len(s)
 
-    # We need to traverse till half of the length of string
-    # as we can get access of the i'th last element from
-    # i'th index.
-    # eg: [0,1,2,3,4,5] => 4th index can be accessed
-    # with the help of 1st index (i==n-i-1)
-    # where n is length of string
-    return all(s[i] == s[n - i - 1] for i in range(end))
 
+    return all(s[i] == s[n - i - 1] for i in range(end))
 
 def is_palindrome_recursive(s: str) -> bool:
     """