Tidy up _from_list
Tidy up _from_list

- remove unused variable
- switch from `range` to `enumerate` for indexed iteration

jparyani/pycapnp,tempbottle/pycapnp,tempbottle/pycapnp,jparyani/pycapnp,SymbiFlow/pycapnp,rcrowder/pycapnp,jparyani/pycapnp,tempbottle/pycapnp,rcrowder/pycapnp,jparyani/pycapnp,SymbiFlow/pycapnp,rcrowder/pycapnp,SymbiFlow/pycapnp,SymbiFlow/pycapnp,tempbottle/pycapnp,rcrowder/pycapnp