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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 _collect_fields(self):
 """ Iterate over all Field objects within, including multi fields. """

        for f in itervalues(self.properties.to_dict()):
            yield f
            # multi fields
            if hasattr(f, 'fields'):
                for inner_f in itervalues(f.fields.to_dict()):
                    yield inner_f
            # nested and inner objects
            if hasattr(f, '_collect_fields'):
                for inner_f in f._collect_fields():
                    yield inner_f