The flexibility of this system also entails that you can in effect define a completely new programming language, describe the process of creating Python bytecode from your custom source, and have clients transparently `import` source in the other language as a result. Or you can define an import process that grabs code from the Internet (not that it would be a good idea...).
If you mean "by explicitly specifying a relative path, and having it be interpreted according to the path of the current module's source code", well first you have to consider that the current module isn't required to have source code. But if it does, then generally it will have been loaded with the default mechanism, which means the module object will have a `__file__` attribute with an absolute path, and you just set your path relative to that.