## Camel-to-snake-case
### Instructions
Write a function that converts a string from `CamelCase` to `snake_case` .
Camel case is the practice of writing phrases without spaces or punctuation, it indicates the separation of two words with a single capitalized letter. Snake case is a style of writing in which each space is replaced by an underscore (_) character.
Here are some rules for you to follow:
- If the string is empty, return an empty string.
- If the string is not `CamelCase` , return the string unchanged.
- If the string is `CamelCase` , return the `snake_case` version of the string.
Basic `CamelCase` Capitalization Rules:
- The first letter must be capitalized.
- The word must not have two capitalized letters together (CamelCAse) nor end with a capitalized letter (CamelCasE).
- No numbers or punctuations are allowed in the word at any place (CamelCase1more).
### Expected function
```go
func CamelToSnakeCase(s string) string{
//Your code here
}
```
### Usage
Here is a possible program to test your function:
```go
package main
import "fmt"
func main() {
fmt.Println(CamelToSnakeCase("HelloWorld"))
fmt.Println(CamelToSnakeCase("helloWorld"))
fmt.Println(CamelToSnakeCase("CamelToSnakeCase"))
fmt.Println(CamelToSnakeCase("132322"))
}
```
and the output should be:
```console
$ go run .
Hello_World
helloWorld
Camel_To_Snake_Case
132322
```
