def is_satisfied(label, signal_values):
    """
    Do signal values satisfy the label?

    >>> is_satisfied({'r':True}, dict())
    True
    >>> is_satisfied(dict(), {'r':True})
    True
    >>> is_satisfied({'r':True}, {'r':True, 'g':False})
    True
    >>> is_satisfied({'r':True, 'g':False}, {'g':False})
    True
    >>> is_satisfied({'g':False}, {'r':True})
    True
    """

    for var, val in signal_values.items():
        if var not in label:
            continue
        if label[var] != val:
            return False
    return True