this is one of sylvia's "juvinelia" poems. it seems that she's following a similar format to what dylan thomas used in 'do not go gentle into that good night'. and we do know that sylvia was familiar with dylan thomas. her teachers would often give advice on how she can improve her poetry, so any format could have even been on advice from a lecturer. but remember; some of sylvia's juvinelia was written when she was as a young as her early teens, so this may have simply been her own skill at a very young age.