Let $\mathbf { x }$ and $\mathbf { y }$ be real numbers.
$$2 ^ { x } - 2 ^ { -y } \left( 2 ^ { x+y } - 2 \right)$$
Which of the following is this expression equal to?\\
A) $2 ^ { x+1 }$\\
B) $2 ^ { y-x }$\\
C) $2 ^ { -y+1 }$\\
D) $\frac { 2 } { 9 }$\\
E) $\frac { 4 } { 9 }$