def __init__(self, handlers=None):
        """
        Parameters
        -----------
        handlers: Mapping[Type, DataModel] or None
            Optionally provide the initial handlers mapping.
        """
        # { numba type class -> model factory }
        self._handlers = handlers or {}
        # { numba type instance -> model instance }
        self._cache = weakref.WeakKeyDictionary()

        Parameters
        -----------
        handlers: Mapping[Type, DataModel] or None
            Optionally provide the initial handlers mapping.
        
numba/core/datamodel/manager.py