def METHOD_NAME(self, lits):
    """
    Add a new clause to set of clauses.
    INPUT:
    - ``lits`` - a tuple of integers != 0
    .. note::
        If any element ``e`` in ``lits`` has ``abs(e)`` greater
        than the number of variables generated so far, then new
        variables are created automatically.
    EXAMPLES::
        sage: S=SAT(solver="LP"); S
        an ILP-based SAT Solver
        sage: for u,v in graphs.CycleGraph(6).edges(sort=False, labels=False):
        ....:     u,v = u+1,v+1
        ....:     S.add_clause((u,v))
        ....:     S.add_clause((-u,-v))
    """
    if 0 in lits:
        raise ValueError("0 should not appear in the clause: {}".format(lits))
    p = self._LP
    p.add_constraint(p.sum(self._vars[x] if x>0 else 1-self._vars[-x] for x in lits)
                     >=1)