One of the fun parts of Ruby is that you can extend all the standard types by extending their class. In this challenge, you need to give Ruby Strings a swap_case() function, which will return a new string with all upper case characters swapped for lower case characters, and vice versa. Any non-alphabetic characters should be kept as they are.

Examples

"Hello".swap_case ➞ "hELLO"

"2 4 6 8 WHO DO WE APPRECIATE?".swap_case ➞ "2 4 6 8 who do we appreciate?"

"aBcD".swap_case.swap_case ➞ "aBcD"

Notes

• swap_case() should not alter the original string.
• Although you can add new functions to the standard data types, it's not generally a good idea in large projects!
• Do not use swapcase().