How to reassign a variable in an imported file?

Question

Sass

SASS is imported (connected) to its file, from a third-party provider. It has the variable $urlPatch (the path to the images) declared at the beginning of the document. How can I reassign it when importing (by changing the paths in the images)?

Now I just assign a variable with the same name before the import line, and delete the variable declaration line in the imported file. But this has to be done every time a third party vendor updates their SASS. How it can be reassigned is not clear.