An internal function to help prepare_output() process lists of data.
Arguments
- output
 A list-like object originating from
daedalus_internal()and partially processed withinprepare_output().- new_vaccinations
 A list object of new vaccination data origination in
daedalus_internal().- timesteps
 A vector of timesteps, typically starting with 0.
- labels
 A list of labels to be applied to the data.