Multiple issues detected when running `devtools::check()`

[GaryBAYLOR]

Issues when running devtools::check():

• Fix the duplicate chunk label issue in the vignette described in the following error message when running devtools::check(). This should be easy to fix.

  E  creating vignettes (10.2s)
  --- re-building ‘intro_CVtreeMLE.Rmd’ using rmarkdown
  Error: processing vignette 'intro_CVtreeMLE.Rmd' failed with diagnostics:
  Duplicate chunk label 'plot sim_mixture_results', which has been used for the chunk:
  mixture_plots <- plot_mixture_results(
   v_intxn_results = niehs_results$`V-Specific Mix Results`, 
   hjust = 0.8)
  mixture_plots$X5X7
  Error: tangling vignette 'intro_CVtreeMLE.Rmd' failed with diagnostics:
  Duplicate chunk label 'plot sim_mixture_results', which has been used for the chunk:
  mixture_plots <- plot_mixture_results(
   v_intxn_results = niehs_results$`V-Specific Mix Results`, 
   hjust = 0.8)
  mixture_plots$X5X7
  --- failed re-building ‘intro_CVtreeMLE.Rmd’

• Check and fix the following issue when running devtools::check() which is also related to vignette

  E  creating vignettes (34.4s)
  --- re-building ‘intro_CVtreeMLE.Rmd’ using rmarkdown
  Quitting from lines 114-127 (intro_CVtreeMLE.Rmd) 
  Error: processing vignette 'intro_CVtreeMLE.Rmd' failed with diagnostics:
  could not find function "make_sl3_Task"
  --- failed re-building ‘intro_CVtreeMLE.Rmd’
  
  SUMMARY: processing the following file failed:
   ‘intro_CVtreeMLE.Rmd’
  
  Error: Vignette re-building failed.
  Execution halted
  Error in get_parentpid() : attempt to apply non-function
  Calls: <Anonymous> ... rstudio_stdout -> rstudio_detect -> detect_new -> get_parentpid
  Execution halted

[blind-contours]

Check should pass with only some small warnings that I'm trying to resolve. Vignette has been updated with new visualizations of the fold specific trees, more grounded description of goals, examples of reporting results etc. Duplicate chunk issues have been resolved.