def METHOD_NAME(config, key, base, logger=None):
    """Read the Bandpass parameters from config[key] and return a constructed Bandpass object.
    Parameters:
        config:     A dict with the configuration information.
        key:        The key name in config indicating which object to build.
        base:       The base dict of the configuration.
        logger:     Optionally, provide a logger for logging debug statements. [default: None]
    Returns:
        (bandpass, safe) where bandpass is a Bandpass instance, and safe is whether it is safe to
                         reuse.
    """
    logger = LoggerWrapper(logger)
    logger.debug('obj %d: Start BuildBandpass key = %s',base.get('obj_num',0),key)
    param = config[key]
    # Check for direct value, else get the bandpass type
    if isinstance(param, Bandpass):
        return param, True
    elif isinstance(param, basestring) and (param[0] == '$' or param[0] == '@'):
        return ParseValue(config, key, base, None)
    elif isinstance(param, dict):
        bandpass_type = param.get('type', 'FileBandpass')
    else:
        raise GalSimConfigError("%s must be either a Bandpass or a dict"%key)
    # For these two, just do the usual ParseValue function.
    if bandpass_type in ('Eval', 'Current'):
        return ParseValue(config, key, base, None)
    # Check if we can use the current cached object
    index, index_key = GetIndex(param, base)
    if 'current' in param:
        cbandpass, csafe, cvalue_type, cindex, cindex_key = param['current']
        if cindex == index:
            logger.debug('obj %d: The Bandpass object is already current', base.get('obj_num',0))
            logger.debug('obj %d: index_key = %s, index = %d',base.get('obj_num',0),
                         cindex_key, cindex)
            return cbandpass, csafe
    if bandpass_type not in valid_bandpass_types:
        raise GalSimConfigValueError("Invalid bandpass.type.", bandpass_type,
                                     list(valid_bandpass_types.keys()))
    logger.debug('obj %d: Building bandpass type %s', base.get('obj_num',0), bandpass_type)
    builder = valid_bandpass_types[bandpass_type]
    bandpass, safe = builder.buildBandpass(param, base, logger)
    logger.debug('obj %d: bandpass = %s', base.get('obj_num',0), bandpass)
    param['current'] = bandpass, safe, Bandpass, index, index_key
    return bandpass, safe