Ubuntu pydot failed to call GraphViz.Please install GraphViz 解决方法

如果遇到：

OSError: `pydot` failed to call GraphViz.Please install GraphViz (https://www.graphviz.org/) and ensure that its executables are in the $PATH.

Ubuntu 下解决方法：

sudo apt install graphviz

或者尝试安装：

pip install pydot
pip install pydot-ng
pip install graphviz