In the example that will follow, we will create a new module with as few dependencies as possible.
This will not be the typical case, however. The most frequent situation is where modifications or extensions are needed on an already existing module to fit some specific use cases.
The golden rule is that we shouldn't modify existing modules by changing them directly. It's considered bad practice to modify existing modules. This is especially true for the official modules provided by Odoo. Doing so does not allow a clear separation between the original module code and our modifications, and makes it difficult to apply upgrades.
Instead, we should create new modules to be applied on top of the modules we want to modify, ...