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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 geojson(self, feature_id):
 """Return GeoJSON with ID substituted."""

        if self._geojson.get('id', feature_id) == feature_id:
            return self._geojson
        else:
            geo = self._geojson.copy()
            geo['id'] = feature_id
            return geo