sero_obs size vec vs size mat

[AugustHao]

sero obs function not working because it's expecting a size_mat input (

epiwave/R/create_small_sero_model.R

Line 42 in e145df5

size_mat <- observations$size_mat

) but the data preparation funciton only produces a size vec (

epiwave/R/define_observation_data.R

Line 35 in e145df5

size_vec = size_vec,

)