Filter Repeating Character Strings

Create a function that keeps only strings with repeating identical characters (in other words, it has a set size of 1).

Examples

identical_filter(["aaaaaa", "bc", "d", "eeee", "xyz"])
➞ ["aaaaaa", "d", "eeee"]

identical_filter(["88", "999", "22", "545", "133"])
➞ ["88", "999", "22"]

identical_filter(["xxxxo", "oxo", "xox", "ooxxoo", "oxo"])
➞ []

Notes

• A string with a single character is trivially counted as a string with repeating identical characters.
• If there are no strings with repeating identical characters, return an empty array (see example #3).