no visible bindings during R CMD check

[achubaty]

because these are NOTEs and not WARNINGs/ERRORs, they don't trigger failures during R CMD check:

─  checking R code for possible problems ... [22s/28s] NOTE (27.8s)
   downscale: possible error in downscale_core(xyz = na_xyz, reference =
     reference, obs = obs_periods, obs_ts = obs_years, gcms =
     gcm_ssp_periods, gcm_ssp_ts = gcm_ssp_ts, gcm_hist_ts = gcm_hist_ts,
     ...): unused argument (reference = reference)
   plot_timeSeries: no visible global function definition for ‘data’
   plot_timeSeries: no visible binding for global variable ‘Code’
   plot_timeSeries: no visible binding for global variable ‘yeartime1’
   plot_timeSeries: no visible binding for global variable ‘element1’
   plot_timeSeries: no visible binding for global variable ‘element2’
   plot_timeSeries: no visible binding for global variable ‘yeartime2’
   plot_timeSeries : plot.ensemble: no visible global function definition
     for ‘polygon’
   plot_timeSeries : plot.ensemble: no visible global function definition
     for ‘smooth.spline’
   plot_timeSeries : plot.ensemble: no visible binding for global variable
     ‘element1’
   plot_timeSeries : plot.ensemble: no visible binding for global variable
     ‘element2’
   plot_timeSeries: no visible binding for global variable ‘DATASET’
   plot_timeSeries: no visible global function definition for ‘box’
   plot_timeSeries_input: no visible binding for global variable ‘DATASET’
   Undefined global functions or variables:
     Code DATASET box data element1 element2 polygon smooth.spline
     yeartime1 yeartime2
   Consider adding
     importFrom("graphics", "box", "polygon")
     importFrom("stats", "smooth.spline")
     importFrom("utils", "data")
   to your NAMESPACE file.