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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 _prepdata(self):
 """Adds potentially missing items to the geojson dictionary"""

        
        # if missing, compute and add bbox
        if not self._data.get("bbox"):
            self.update_bbox()

        # if missing, set crs to default crs (WGS84), see http://geojson.org/geojson-spec.html
        if not self._data.get("crs"):
            self._data["crs"] = {"type":"name",
                               "properties":{"name":"urn:ogc:def:crs:OGC:2:84"}}