matplotlib 绘制中文图表

```python
import matplotlib.pyplot as plt
import matplotlib
import matplotlib.font_manager as fm
CJK_CANDIDATES = ["PingFang SC", "Heiti SC", "Hiragino Sans GB",
                  "Songti SC", "STSong", "Arial Unicode MS",
                  "Microsoft YaHei", "SimHei", "WenQuanYi Zen Hei"]
available = {f.name for f in fm.fontManager.ttflist}
for cand in CJK_CANDIDATES:
    if cand in available:
        matplotlib.rcParams["font.sans-serif"] = [cand, "DejaVu Sans"]
        break
matplotlib.rcParams["axes.unicode_minus"] = False
```

执行 python 脚本先 `pyenv activate qlib` 激活环境