docstr: Optimize chunk graph.
code: def optimize(self):
      """
      Optimize chunk graph.
      """
  
file_path: mars/mars/optimization/physical/core.py
imports: from abc import ABC, abstractmethod
  from typing import List, Tuple, Dict, Type
  from ...core import ChunkGraph, ChunkType, OperandType
  from ...utils import build_fuse_chunk
label_desc: Use image node_id 3 for calling the RuntimeOptimizer obj's underlying member method code with example usage: obj.optimize() without return types