@classmethod
def process(cls, config_interp, logger=None):
    """Parse the interp field of the config dict.

        :param config_interp:   The configuration dict for the interp field.
        :param logger:          A logger object for logging debug info. [default: None]

        :returns: an Interp instance
        """
    import piff
    if 'type' not in config_interp:
        raise ValueError("config['interp'] has no type field")
    interp_class = getattr(piff, config_interp['type'])
    kwargs = interp_class.parseKwargs(config_interp, logger)
    interp = interp_class(**kwargs)
    return interp
