Double lettes

[guna7222]

Double letters
The goal of this challenge is to analyze a string to check if it contains two of the same letter in a row. For example, the string "hello" has l twice in a row, while the string "nono" does not have two identical letters in a row.

Define a function named double_letters that takes a single parameter. The parameter is a string. Your function must return True if there are two identical letters in a row in the string, and False otherwise.