class Grape::Util::StackableValues

def [](name)
  inherited_value = inherited_values[name]
  new_value = new_values[name]
  return new_value || [] unless inherited_value
  concat_values(inherited_value, new_value)
end

def []=(name, value)
  new_values[name] ||= []
  new_values[name].push value
end

def concat_values(inherited_value, new_value)
  return inherited_value unless new_value
  inherited_value + new_value
end

def to_hash
  keys.each_with_object({}) do |key, result|
    result[key] = self[key]
  end
end