code: def add_options(ctx):
      
      # Add option
      ctx.add_option(
          '--always',
          action='store_true',
          default=False,
          dest='always',
          help='whether always run tasks.',
      )
  
      # Add option
      ctx.add_option(
          '--check-import',
          action='store_true',
          default=False,
          dest='check_import',
          help='whether import module for dirty checking.',
      )
  
      # Add option
      ctx.add_option(
          '--venv',
          dest='venv',
          help=(
              'virtual environment directory relative path relative to top'
              ' directory.'
          ),
      )
  
      # Add option
      ctx.add_option(
          '--venv-add-version',
          default='1',
          dest='venv_add_version',
          # Convert to int so that the value can be used as boolean
          type=int,
          metavar='0|1',
          help=(
              'whether add full Python version to virtual environment directory'
              ' name. E.g. `.py3.5.1.final.0.64bit`. Default is add.'
          ),
      )
  
      # Add option
      ctx.add_option(
          '--req',
          default=None,
          dest='req_path',
          help='requirements file relative path relative to top directory.',
      )
docs: Add command line options.
  
      :return: None.