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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 export_off(mesh, digits=10):
 """ Export a mesh as an OFF file, a simple text format Parameters mesh : trimesh.Trimesh Geometry to export digits : int Number of digits to include on floats Returns export : str OFF format output """

    # make sure specified digits is an int
    digits = int(digits)
    # prepend a 3 (face count) to each face
    faces_stacked = np.column_stack((np.ones(len(mesh.faces)) * 3,
                                     mesh.faces)).astype(np.int64)
    export = 'OFF\n'
    # the header is vertex count, face count, another number
    export += str(len(mesh.vertices)) + ' ' + str(len(mesh.faces)) + ' 0\n'
    export += util.array_to_string(
        mesh.vertices, col_delim=' ', row_delim='\n', digits=digits) + '\n'
    export += util.array_to_string(
        faces_stacked, col_delim=' ', row_delim='\n')
    return export