You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: git_ref.rb
    path of file: ./repos/gitlabhq/lib/api/validations/validators
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module API
  module Validations
    module Validators
      class GitRef < Grape::Validations::Validators::Bas
    
        def validate_param!(attr_name, params)
          revision = params[attr_name]

          return unless invalid_character?(revision)

          raise Grape::Exceptions::Validation.new(
            params: [@scope.full_name(attr_name)],
            message: 'should be a valid reference path'
          )
        end