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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_implicit_value (value_string):
 """ Returns true iff 'value_string' is a value_string of an implicit feature. """

    assert isinstance(value_string, basestring)
    if value_string in __implicit_features:
        return __implicit_features[value_string]

    v = value_string.split('-')

    if v[0] not in __implicit_features:
        return False

    feature = __implicit_features[v[0]]

    for subvalue in (v[1:]):
        if not __find_implied_subfeature(feature, subvalue, v[0]):
            return False

    return True