Make shell sort support comparable types

sorts/shell_sort.py

@@ -2,8 +2,17 @@
 https://en.wikipedia.org/wiki/Shellsort#Pseudocode
 """
 
+from typing import Any, Protocol, TypeVar
 
-def shell_sort(collection: list[int]) -> list[int]:
+
+class Comparable(Protocol):
+    def __lt__(self, other: Any, /) -> bool: ...
+
+
+T = TypeVar("T", bound=Comparable)
+
+
+def shell_sort[T: Comparable](collection: list[T]) -> list[T]:
     """Pure implementation of shell sort algorithm in Python
     :param collection:  Some mutable ordered collection with heterogeneous
     comparable items inside
@@ -15,9 +24,16 @@ def shell_sort(collection: list[int]) -> list[int]:
     []
     >>> shell_sort([-2, -5, -45])
     [-45, -5, -2]
+    >>> shell_sort(["d", "a", "b", "e", "c"])
+    ['a', 'b', 'c', 'd', 'e']
+    >>> shell_sort([3, 1.5, 2, 0.5])
+    [0.5, 1.5, 2, 3]
+    >>> shell_sort([1, "two", 3])
+    Traceback (most recent call last):
+    ...
+    TypeError: '>' not supported between instances of 'int' and 'str'
     """
     # Marcin Ciura's gap sequence
-
     gaps = [701, 301, 132, 57, 23, 10, 4, 1]
     for gap in gaps:
         for i in range(gap, len(collection)):