def METHOD_NAME(self, sites: Union[int, Iterable]) -> "AbstractHilbert":
    """Returns the hilbert space without the selected sites.
    Not all hilbert spaces support this operation.
    Args:
        sites: a site or list of sites to trace away
    Returns:
        The partially-traced hilbert space. The type of the resulting hilbert space
        might be different from the starting one.
    """
    raise NotImplementedError("Ptrace not implemented for this hilbert space type.")