class ActionController::Parameters

def slice(*keys)

params.slice(:d) # => #
params.slice(:a, :b) # => #1, "b"=>2} permitted: false>
params = ActionController::Parameters.new(a: 1, b: 2, c: 3)

don't exist, returns an empty hash.
includes only the given +keys+. If the given +keys+
Returns a new +ActionController::Parameters+ instance that 
def slice(*keys)
  new_instance_with_inherited_permitted_status(@parameters.slice(*keys))
end