'Add a new clause to the theory.
Examples
>>> from sympy.logic.algorithms.dpll2 import SATSolver
>>> l = SATSolver([{2, -3}, {1}, {3, -3}, {2, -2},
... {3, -2}], {1, 2, 3}, set())
>>> l.num_learned_clauses
0
>>> l.clauses
[[2, -3], [1], [3, -3], [2, -2], [3, -2]]
>>> l.sentinels
{-3: {0, 2}, -2: {3, 4}, 2: {0, 3}, 3: {2, 4}}
>>> l._simple_add_learned_clause([3])
>>> l.clauses
[[2, -3], [1], [3, -3], [2, -2], [3, -2], [3]]
>>> l.sentinels
{-3: {0, 2}, -2: {3, 4}, 2: {0, 3}, 3: {2, 4, 5}}'

def _simple_add_learned_clause(self, cls):

    cls_num = len(self.clauses)
    self.clauses.append(cls)
    for lit in cls:
        self.occurrence_count[lit] += 1
    self.sentinels[cls[0]].add(cls_num)
    self.sentinels[cls[(-1)]].add(cls_num)
    self.heur_clause_added(cls)
