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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 actualize_source_type (self, sources, prop_set):
 """ Helper for 'actualize_sources'. For each passed source, actualizes it with the appropriate scanner. Returns the actualized virtual targets. """

        assert is_iterable_typed(sources, VirtualTarget)
        assert isinstance(prop_set, property_set.PropertySet)
        result = []
        for i in sources:
            scanner = None

# FIXME: what's this?
#            if isinstance (i, str):
#                i = self.manager_.get_object (i)

            if i.type ():
                scanner = b2.build.type.get_scanner (i.type (), prop_set)

            r = i.actualize (scanner)
            result.append (r)

        return result