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: uniqueness_matcher.rb
    path of file: ./repos/shoulda-matchers/spec/support/unit/create_model_arguments
    
    the code of the file until where you have to start completion: module UnitTests
  module CreateModelArguments
    class UniquenessMatcher < Basic
      def self.normalize_attribute(attribute)
        if attribute.is_a?(Hash)
          Attribute.new(attribute)
        else
          A
    
      def columns
        attributes.inject({}) do |options, attribute|
          options.merge(
            attribute.name => {
              type: attribute.column_type,
              options: attribute.column_options,
            },
          )
        end
      end