imports issues

[JeffFessler]

From ExplicitImports.jl:

However, module PERK has 1 self-qualified access:

•  krr_train was accessed as PERK.krr_train inside PERK at
   /Users/fessler/.julia/packages/PERK/V4Z8Q/src/holdout.jl:105:30

Additionally, module PERK accesses 4 non-public names:

•  Dual is not public in ForwardDiff but it was accessed via ForwardDiff at
   /Users/fessler/.julia/packages/PERK/V4Z8Q/src/krr.jl:211:51
•  GLOBAL_RNG is not public in Random but it was accessed via Random at
   /Users/fessler/.julia/packages/PERK/V4Z8Q/src/estimation.jl:85:24
•  partials is not public in ForwardDiff but it was accessed via ForwardDiff at
   /Users/fessler/.julia/packages/PERK/V4Z8Q/src/krr.jl:215:21
•  value is not public in ForwardDiff but it was accessed via ForwardDiff at
   /Users/fessler/.julia/packages/PERK/V4Z8Q/src/krr.jl:213:21