Package check result: ERROR

Check: examples, Result: ERROR
  Running examples in ‘mlexperiments-Ex.R’ failed
  The error most likely occurred in:
  
  > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
  > ### Name: LearnerKnn
  > ### Title: LearnerKnn R6 class
  > ### Aliases: LearnerKnn
  > 
  > ### ** Examples
  > 
  > LearnerKnn$new()
  Error: Package "class" must be installed to use 'learner = "LearnerKnn"'.
  Execution halted