def __call__(self, parser, namespace, values, option_strings=None):  # @UnusedVariable
        # Need None here incase `argparse.SUPPRESS` was supplied for `dest`
        dest = getattr(namespace, self.dest, None)
        if(not hasattr(dest, 'extend') or dest == self.default):
            dest = []
            setattr(namespace, self.dest, dest)
            # if default isn't set to None, this method might be called
            # with the default as `values` for other arguments which
            # share this destination.
            parser.set_defaults(**{self.dest: None})

        try:
            dest.extend(values)
        except __HOLE__:
            dest.append(values)
dataset/ETHPy150Open conan-io/conan/conans/client/command.py/Extender.__call__