new_contents: import os
  
  class Cd:
      aliases = 'cd'
      description = 'Change working directory'
  
      def matches(self, expression):
          parts = expression.split()
  
          return parts[0] == 'cd' and len(parts) == 2
  
      def execute(self, expression):
          target = expression.split()[1]
  
          os.chdir(os.path.join(os.getcwd(), target))
  
  
subject: Implement cd command