Function new_mut 

pub fn new_mut<DynSliceFromType>(value: &mut [DynSliceFromType]) -> SliceMut<'_>
where
    Dyn: Pointee<Metadata = DynMetadata<Dyn>>,
    DynSliceFromType: 'static + Debug,

Create a mutable dyn slice from a mutable slice of a type that implements Debug.