code: def entails(expr, formula_set=None):
      """
      Check whether the given expr_set entail an expr.
      If formula_set is empty then it returns the validity of expr.
  
      Examples
      ========
  
      >>> from sympy.abc import A, B, C
      >>> from sympy.logic.inference import entails
      >>> entails(A, [A >> B, B >> C])
      False
      >>> entails(C, [A >> B, B >> C, A])
      True
      >>> entails(A >> B)
      False
      >>> entails(A >> (B >> A))
      True
  
      References
      ==========
  
      .. [1] https://en.wikipedia.org/wiki/Logical_consequence
  
      """
      if formula_set:
          formula_set = list(formula_set)
      else:
          formula_set = []
      formula_set.append(Not(expr))
      return not satisfiable(And(*formula_set))
  
imports: from sympy.logic.boolalg import And, Not, conjuncts, to_cnf, BooleanFunction
  from sympy.core.sorting import ordered
  from sympy.core.sympify import sympify
  from sympy.external.importtools import import_module
label_desc: Use image node_id 5 for calling a global function with example usage: entails(expr, formula_set) and returns: unknown