old_contents: from robber import expect
  from base import Base
  
  class Contain(Base):
      """
      expect({'key': value}).to.contain('key')
      expect([1, 2, 3]).to.contain(2)
      """
      def matches(self):
          return self.expected in self.actual
  
      def failure_message(self):
          return 'Expected {} to contain {}'.format(self.actual, self.expected)
  
  expect.register('contain', Contain)
  
new_contents: from robber import expect
  from base import Base
  
  class Contain(Base):
      """
      expect({'key': value}).to.contain('key')
      expect([1, 2, 3]).to.contain(2)
      """
      def matches(self):
          return self.expected in self.actual
  
      def failure_message(self):
          return 'Expected {0} to contain {1}'.format(self.actual, self.expected)
  
  expect.register('contain', Contain)
  
subject: Add numbers in string format For compatibility with python 2.6