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: mock.rb
    path of file: ./repos/mocha/lib/mocha
    
    the code of the file until where you have to start completion: require 'ruby2_keywords'
require 'mocha/expectation'
require 'mocha/expectation_list'
require 'mocha/invocation'
require 'mocha/names'
require 'mocha/receivers'
require 'mocha/method_matcher'
require 'mocha/parameters_matcher'
require 'mocha/argument_iterator'
require 'mocha/expectation_error_factory'

module Mocha
  # Tra
    
    def expects(method_name_or_hash, backtrace = nil)
      expectation = nil
      iterator = ArgumentIterator.new(method_name_or_hash)
      iterator.each do |*args|
        method_name = args.shift
        ensure_method_not_already_defined(method_name)
        expectation = Expectation.new(self, method_name, backtrace)
        expectation.in_sequence(@mockery.sequences.last) if @mockery.sequences.any?
        expectation.returns(args.shift) unless args.empty?
        @expectations.add(expectation)
      end
      expectation
    end