Parse a portion of command line arguments with the early parser.

        This method relies on ``context.argv`` and ``context.early_parser``
        and produces ``context.early_args``.

        The ``context.early_args`` object is the return value from argparse.
        It is the dict/object like namespace object.

def preparse(self, context):
        """
        Parse a portion of command line arguments with the early parser.

        This method relies on ``context.argv`` and ``context.early_parser``
        and produces ``context.early_args``.

        The ``context.early_args`` object is the return value from argparse.
        It is the dict/object like namespace object.
        """
        context.early_args, unused = (
            context.early_parser.parse_known_args(context.argv))