  Hansel's lemma states that $\sum_{H\in \mathcal{H}}|H| \geq n \log_2 n$ holds
where $\mathcal{H}$ is a collection of bipartite graphs covering all the edges
of $K_n$. We generalize this lemma to the corresponding multigraph covering
problem and the graphon covering problem. We also prove an upper bound on
$\sum_{H\in \mathcal{H}}|H|$ which shows that our generalization is
asymptotically tight in some sense.
