How to use the gitdb.base.OPackInfo function in gitdb

delta_info = data[data_rela_offset:total_rela_offset]
    # BASE OBJECT
    else:
        # assume its a base object
        total_rela_offset = data_rela_offset
    # END handle type id
    abs_data_offset = offset + total_rela_offset
    if as_stream:
        stream = DecompressMemMapReader(buffer(data, total_rela_offset), False, uncomp_size)
        if delta_info is None:
            return abs_data_offset, OPackStream(offset, type_id, uncomp_size, stream)
        else:
            return abs_data_offset, ODeltaPackStream(offset, type_id, uncomp_size, delta_info, stream)
    else:
        if delta_info is None:
            return abs_data_offset, OPackInfo(offset, type_id, uncomp_size)
        else:
            return abs_data_offset, ODeltaPackInfo(offset, type_id, uncomp_size, delta_info)
        # END handle info

"""Uses size info of its stream, delaying reads"""

    def __new__(cls, sha, type, size, stream, *args, **kwargs):
        """Helps with the initialization of subclasses"""
        return tuple.__new__(cls, (sha, type, size, stream))

    #{ Stream Reader Interface

    @property
    def size(self):
        return self[3].size

    #} END stream reader interface


class OPackStream(OPackInfo):

    """Next to pack object information, a stream outputting an undeltified base object
    is provided"""
    __slots__ = tuple()

    def __new__(cls, packoffset, type, size, stream, *args):
        """Helps with the initialization of subclasses"""
        return tuple.__new__(cls, (packoffset, type, size, stream))

    #{ Stream Reader Interface
    def read(self, size=-1):
        return self[3].read(size)

    @property
    def stream(self):
        return self[3]

delta_info = data[data_rela_offset:total_rela_offset]
    # BASE OBJECT
    else:
        # assume its a base object
        total_rela_offset = data_rela_offset
    # END handle type id
    abs_data_offset = offset + total_rela_offset
    if as_stream:
        stream = DecompressMemMapReader(buffer(data, total_rela_offset), False, uncomp_size)
        if delta_info is None:
            return abs_data_offset, OPackStream(offset, type_id, uncomp_size, stream)
        else:
            return abs_data_offset, ODeltaPackStream(offset, type_id, uncomp_size, delta_info, stream)
    else:
        if delta_info is None:
            return abs_data_offset, OPackInfo(offset, type_id, uncomp_size)
        else:
            return abs_data_offset, ODeltaPackInfo(offset, type_id, uncomp_size, delta_info)
        # END handle info

    @property
    def type(self):
        return type_id_to_type_map[self[1]]

    @property
    def type_id(self):
        return self[1]

    @property
    def size(self):
        return self[2]

    #} END interface


class ODeltaPackInfo(OPackInfo):

    """Adds delta specific information,
    Either the 20 byte sha which points to some object in the database,
    or the negative offset from the pack_offset, so that pack_offset - delta_info yields
    the pack offset of the base object"""
    __slots__ = tuple()

    def __new__(cls, packoffset, type, size, delta_info):
        return tuple.__new__(cls, (packoffset, type, size, delta_info))

    #{ Interface
    @property
    def delta_info(self):
        return self[3]
    #} END interface