def enumeration_ask(X, e, bn):
    """Return the conditional probability distribution of variable X
    given evidence e, from BayesNet bn. [Fig. 14.9]
    >>> enumeration_ask('Burglary', dict(JohnCalls=T, MaryCalls=T), burglary
    ...  ).show_approx()
    'False: 0.716, True: 0.284'"""
    assert X not in e, "Query variable must be distinct from evidence"
    Q = ProbDist(X)
    for xi in bn.variable_values(X):
        Q[xi] = enumerate_all(bn.vars, extend(e, X, xi), bn)
    return Q.normalize()
Return the conditional probability distribution of variable X
    given evidence e, from BayesNet bn. [Fig. 14.9]
    >>> enumeration_ask('Burglary', dict(JohnCalls=T, MaryCalls=T), burglary
    ...  ).show_approx()
    'False: 0.716, True: 0.284