def __init__(self,
converter_caps=None,
pre_converter=None,
registry=None,
externalizer=None,
source_ver=None,
target_ver=None):
global _global_registry
assert ((source_ver is None) and (target_ver is None)) \
or ((source_ver is not None) and (target_ver is not None))
self.converter_capabilities = converter_caps or DEFAULT_CONVERTER_CAPS
self._pre_converter = pre_converter and IConverter(pre_converter)
self._registry = IRegistry(registry) if registry else _global_registry
self._externalizer = externalizer and IExternalizer(externalizer)
self._source_ver = source_ver
self._target_ver = target_ver
self.reset()
