class_docstr: Class for representing a SAT solver capable of
   finding a model to a boolean theory in conjunctive
   normal form.
class_docstr_tok: ["Class","for","representing","a","SAT","solver","capable","of","finding","a","model","to","a","boolean","theory","in","conjunctive","normal","form","."]
docstr: Check if a literal is a sentinel of a given clause.
  
  Examples
  ========
  
  >>> from sympy.logic.algorithms.dpll2 import SATSolver
  >>> l = SATSolver([{2, -3}, {1}, {3, -3}, {2, -2},
  ... {3, -2}], {1, 2, 3}, set())
  >>> next(l._find_model())
  {1: True, 2: False, 3: False}
  >>> l._is_sentinel(2, 3)
  True
  >>> l._is_sentinel(-3, 1)
  False
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code: def _is_sentinel(self, lit, cls):
      """Check if a literal is a sentinel of a given clause.
  
      Examples
      ========
  
      >>> from sympy.logic.algorithms.dpll2 import SATSolver
      >>> l = SATSolver([{2, -3}, {1}, {3, -3}, {2, -2},
      ... {3, -2}], {1, 2, 3}, set())
      >>> next(l._find_model())
      {1: True, 2: False, 3: False}
      >>> l._is_sentinel(2, 3)
      True
      >>> l._is_sentinel(-3, 1)
      False
  
      """
      return cls in self.sentinels[lit]
  
imports: from collections import defaultdict
  from heapq import heappush, heappop
  from sympy.core.sorting import ordered
  from sympy.assumptions.cnf import EncodedCNF
  from sympy.logic.algorithms.lra_theory import LRASolver
label_desc: Use image node_id 7 for calling the SATSolver obj's underlying member method code with example usage: obj._is_sentinel(lit, cls) and returns: unknown