Chapter 9

1. It is bad practice to copy and paste the OpenZeppelin library code and use it in your project. You must install the OpenZeppelin npm package in your project. You can stick to using a specific version of the library files in your project. 
2. You should not make any modifications in the OpenZeppelin library files present in the node_modules folder. These library files are thoroughly tested, and so if you need a modified version of the files, copy it from the library and maintain your version separately in your project.
3. Sometimes, there are requirements for which you do not need some of the functions of the OpenZeppelin library files. In such cases, you can override specific functions in your implementation to always revert a transaction. This is the best way to handle and remove these functions from the library contract files.
4. You can use the mathematical...