fn clone_into(&self, target: &mut String) {
        let mut b = mem::take(target).into_bytes();
        self.as_bytes().clone_into(&mut b);
        *target = unsafe { String::from_utf8_unchecked(b) }
    }
Replaces first N matches of a pattern with another string.

`replacen` creates a new [`String`], and copies the data from this string slice into it.
While doing so, it attempts to find matches of a pattern. If it finds any, it
replaces them with the replacement string slice at most `count` times.

# Examples

Basic usage:

```
let s = "foo foo 123 foo";
assert_eq!("new new 123 foo", s.replacen("foo", "
benchmarks/haystacks/code/rust-library.rs