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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 closer_than(self, mesh, radius):
 """ Check for proximity of points in the ``mesh``. :param mesh: :class:`openquake.hazardlib.geo.mesh.Mesh` instance. :param radius: Proximity measure in km. :returns: Numpy array of boolean values in the same shape as the mesh coordinate arrays with ``True`` on indexes of points that are not further than ``radius`` km from this point. Function :func:`~openquake.hazardlib.geo.geodetic.distance` is used to calculate distances to points of the mesh. Points of the mesh that lie exactly ``radius`` km away from this point also have ``True`` in their indices. """

        dists = geodetic.distance(self.longitude, self.latitude, self.depth,
                                  mesh.lons, mesh.lats,
                                  0 if mesh.depths is None else mesh.depths)
        return dists <= radius