dimensions \(l_{1} \times d_{1}\) and \(l_{2} \times d_{2}\), such that \(l_{1} \times l_{2} = l\) and
\(d_{1} + d_{2} = d\) (with the product for the lengths, this ends up being way smaller). The embedding for time
step \(j\) in E is obtained by concatenating the embeddings for timestep \(j \% l1\) in E1 and \(j // l1\)
in E2.
