https://discourse.julialang.org/t/lag-lead-in-panel-data/48140/6 https://discourse.julialang.org/t/create-lead-and-lag-variable-in-dataframe/8658/9 https://github.com/JuliaArrays/ShiftedArrays.jl/pull/37 https://stackoverflow.com/questions/61038354/create-lag-lead-time-series-with-by-groups-in-julia
