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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 get_pmeshes(self, sites, permutation=None):
 """ Returns the pmesh strings used for jmol to show this geometry. """

        pmeshes = []
        # _vertices = [site.coords for site in sites]
        if permutation is None:
            _vertices = [site.coords for site in sites]
        else:
            _vertices = [sites[ii].coords for ii in permutation]
        _face_centers = []
        number_of_faces = 0
        for face in self._faces:
            if len(face) in [3, 4]:
                number_of_faces += 1
            else:
                number_of_faces += len(face)

            _face_centers.append(np.array([np.mean([_vertices[face_vertex][ii]
                                                    for face_vertex in face])
                                           for ii in range(3)]))

        out = '{}\n'.format(len(_vertices) + len(_face_centers))
        for vv in _vertices:
            out += '{:15.8f} {:15.8f} {:15.8f}\n'.format(vv[0], vv[1], vv[2])
        for fc in _face_centers:
            out += '{:15.8f} {:15.8f} {:15.8f}\n'.format(fc[0], fc[1], fc[2])
        out += '{:d}\n'.format(number_of_faces)
        for iface, face in enumerate(self._faces):
            if len(face) == 3:
                out += '4\n'
            elif len(face) == 4:
                out += '5\n'
            else:
                for ii in range(len(face)):
                    out += '4\n'
                    out += '{:d}\n'.format(len(_vertices) + iface)
                    out += '{:d}\n'.format(face[ii])
                    out += '{:d}\n'.format(face[np.mod(ii + 1, len(face))])
                    out += '{:d}\n'.format(len(_vertices) + iface)
            if len(face) in [3, 4]:
                for face_vertex in face:
                    out += '{:d}\n'.format(face_vertex)
                out += '{:d}\n'.format(face[0])
        pmeshes.append({"pmesh_string": out})
        return pmeshes