'Check if a clause is satisfied by the current variable setting.
Examples
>>> from sympy.logic.algorithms.dpll2 import SATSolver
>>> l = SATSolver([{1}, {-1}], {1}, set())
>>> try:
...     next(l._find_model())
... except StopIteration:
...     pass
>>> l._clause_sat(0)
False
>>> l._clause_sat(1)
True'

def _clause_sat(self, cls):

    for lit in self.clauses[cls]:
        if (lit in self.var_settings):
            return True
    return False
