7. The graph of the function $f(x)=\sin 2x$ is shifted to the left by $\frac{\pi}{3}$ units, and then the horizontal coordinates of each point on the resulting graph are compressed to $\frac{1}{2}$ of their original values. The analytical expression of the resulting function is . $\qquad$
7. $\sin \left(4 x+\frac{2}{3} \pi\right)$