def METHOD_NAME(self):
    r"""
    Return the hook product for the poset.
    TESTS::
        sage: from sage.combinat.posets.d_complete import DCompletePoset
        sage: P = DCompletePoset(DiGraph({0: [1, 2], 1: [3], 2: [3], 3: []}))
        sage: P.hook_product()
        12
        sage: P = DCompletePoset(posets.YoungDiagramPoset(Partition([3,2,1]),       # optional - sage.combinat
        ....:                    dual=True))
        sage: P.hook_product()                                                      # optional - sage.combinat
        45
    """
    if not self._hasse_diagram:
        return ZZ.one()
    return ZZ(prod(self._hooks.values()))