Is function $f(\theta)=\sum_{i=1}^{k}\sum_{j \neq i}||\theta_i||_2^2 ||\theta_j||_2^2$ a quasi-convex function?

Question

I would like to get some help about the next problem: Is function $f(\theta)=\sum_{i=1}^{k}\sum_{j \neq i}||\theta_i||_2^2 ||\theta_j||_2^2$ a quasi-convex function? Where $\theta_i \in R^n$, $||\cdot||^2_2$ is the square of 2-norm, $k \geq 2$.