pub fn as_raw_faststr(&self) -> FastStr {
        match &self.raw {
            JsonSlice::Raw(r) => unsafe { FastStr::new_u8_slice_unchecked(r) },
            JsonSlice::FastStr(f) => f.clone(),
        }
    }
Export the raw json text as faststr.

# Note
If the input json is not bytes or faststr, there will be a string copy.

# Examples

```
use faststr::FastStr;
use sonic_rs::LazyValue;

let lv: LazyValue = sonic_rs::get(r#"{"a": "hello world"}"#, &["a"]).unwrap();
// will copy the raw_str into a new faststr
assert_eq!(lv.as_raw_faststr(), "\"hello world\"");

let fs = FastStr::new(r#"{"a": "hello world"}"#);
let lv: LazyValue = sonic_rs::get(&fs, &["a"]).unwrap();
assert_eq!(lv.as_raw_faststr(), "\"hello world\""); // zero-copy
```
src/lazyvalue/value.rs