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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 expand_subfeatures(properties, dont_validate = False):
 """ Make all elements of properties corresponding to implicit features explicit, and express all subfeature values as separate properties in their own right. For example, the property gcc-2.95.2-linux-x86 might expand to <toolset>gcc <toolset-version>2.95.2 <toolset-os>linux <toolset-cpu>x86 properties: A sequence with elements of the form <feature>value-string or just value-string in the case of implicit features. : dont_validate: If True, no validation of value string will be done. """

    if __debug__:
        from .property import Property
        assert is_iterable_typed(properties, Property)
        assert isinstance(dont_validate, int)  # matches bools
    result = []
    for p in properties:
        # Don't expand subfeatures in subfeatures
        if p.feature.subfeature:
            result.append (p)
        else:
            result.extend(__expand_subfeatures_aux (p, dont_validate))

    return result