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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 _IDW(self, latitude, longitude, radius=1):
 """ Return the interpolated elevation at a point. Load the correct tile for latitude and longitude given. If the tile doesn't exist, return None. Otherwise, call the tile's Inverse Distance Weighted function and return the elevation. Args: latitude: float with the latitude in decimal degrees longitude: float with the longitude in decimal degrees radius: int of 1 or 2 indicating the approximate radius of adjacent cells to include Returns: a float of the interpolated elevation with the same unit as the .hgt file (meters) """

        tile = self.get_file(latitude, longitude)
        if tile is None:
            return None
        return tile._InverseDistanceWeighted(latitude, longitude, radius)