Value of $\frac{\sum_{k=0}^{6} \csc^{2}(\theta + \frac{k\pi}{7})}{7\csc^{2}(7\theta)}$

Question

At $$\theta=\frac{\pi}{8}$$

I tried using Euler notation($e^{i\theta}$ form) but was of no help.I breaked the expression in parts but just to make it more cumbersome.

Any help !!