fn as_mut_slice(&mut self) -> &mut [C64] {
        &mut self.data[..]
    }
Mutable slice of `self.data`

# Examples
```rust
use peroxide::fuga::*;
use peroxide::complex::matrix::*;

let mut a = cmatrix(vec![C64::new(1f64, 1f64),
C64::new(2f64, 2f64),
C64::new(3f64, 3f64),
C64::new(4f64, 4f64)],
2, 2, Row
);
let mut b = a.as_mut_slice();
b[1] = C64::new(5f64, 5f64);
assert_eq!(b, &[C64::new(1f64, 1f64),
C64::new(5f64, 5f64),
C64::new(3f64, 3f64),
C64::new(4f64, 4f64)]);
assert_eq!(a, cmatrix(vec![C64::new(1f64, 1f64),
C64::new(5f64, 5f64),
C64::new(3f64, 3f64),
C64::new(4f64, 4f64)],
2, 2, Row));
```
src/complex/matrix.rs