Let $S_n$ be the symmetric group over $\{1,2,\ldots,n\}$. How to return elements of length $m$ in $S_n$ using Sage? I try to find such function in Sage but didn't find one. Thank you very much.

Edit: $S_n$ is the Coxeter group of type $A$ generated by $s_1=(12), \ldots, s_{n-1}=(n-1,n)$. The length of an element $w \in S_n$ is the least number of simple reflections $s_i$ occurring in any expression for $w$.