def METHOD_NAME(expr, formula_set={}):
    """
    Check whether the given expr_set entail an expr.
    If formula_set is empty then it returns the validity of expr.
    Examples
    ========
    >>> 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
    ==========
    * https://en.wikipedia.org/wiki/Logical_consequence
    """
    formula_set = list(formula_set)
    formula_set.append(Not(expr))
    return not satisfiable(And(*formula_set))