class ActionController::Parameters

def transform_values(&block)

# => {"a"=>2, "b"=>4, "c"=>6}
params.transform_values { |x| x * 2 }
params = ActionController::Parameters.new(a: 1, b: 2, c: 3)

running +block+ once for every value. The keys are unchanged.
Returns a new ActionController::Parameters with the results of 
def transform_values(&block)
  if block
    new_instance_with_inherited_permitted_status(
      @parameters.transform_values(&block)
    )
  else
    @parameters.transform_values
  end
end