def __init__(self, typepath, pythonpath):
        self._compile_queue = None
        self._typepath = typepath
        self._pythonpath = pythonpath
        self.modules = None # maps ast node -> usermodulemt object
        self._loaded_modules = None # maps fn -> usermodulemt object
        self._module_filenames = None # maps ast module -> fn
        self._closure_results = None
        self.type_info = None