Package check result: ERROR

Check: CRAN incoming feasibility, Result: NOTE
  Maintainer: ‘Torsten Pook <torsten.pook@wur.nl>’
  
  New maintainer:
    Torsten Pook <torsten.pook@wur.nl>
  Old maintainer(s):
    Torsten Pook <torsten.pook@uni-goettingen.de>
  
  Suggests or Enhances not in mainstream repositories:
    alstructure, visPedigree, miraculix, RandomFieldsUtils, MoBPSmaps
  Availability using Additional_repositories specification:
    alstructure         yes   https://tpook92.github.io/drat/
    visPedigree         yes   https://tpook92.github.io/drat/
    miraculix           yes   https://tpook92.github.io/drat/
    RandomFieldsUtils   yes   https://tpook92.github.io/drat/
    MoBPSmaps           yes   https://tpook92.github.io/drat/

Check: examples, Result: ERROR
  Running examples in ‘MoBPS-Ex.R’ failed
  The error most likely occurred in:
  
  > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
  > ### Name: ogc.mobps
  > ### Title: Breeding function
  > ### Aliases: ogc.mobps
  > 
  > ### ** Examples
  > 
  > population <- creating.diploid(nsnp=1000, nindi=100, n.additive = 10)
  Both sexes in the cohort. Added _M, _F to cohort names!
  Successfully generated cohort: Cohort_1_M
  Database position: 1 (gen), 1 (sex), 1 (first), 50 (last).
  Successfully generated cohort: Cohort_1_F
  Database position: 1 (gen), 2 (sex), 1 (first), 50 (last).
  Derive genomic values of founders. 
  > population <- breeding.diploid(population, breeding.size=100, selection.size=c(25,25),
  + ogc = TRUE)
  No individuals for selection provided (male side). Use last available.
  No individuals for selection provided (female side). Use last available.
  Start selection procedure.
  Selection male size:
  Select 25 individuals out of  50.
  Selection female size:
  Select 25 individuals out of  50.
  Warning in breeding.diploid(population, breeding.size = 100, selection.size = c(25,  :
    Optimum genetic contribution only possible if optiSel R-package is installed. Skip OGC! 
  
  Error in breeding.diploid(population, breeding.size = 100, selection.size = c(25,  : 
    object 'contribution' not found
  Execution halted