Basically, this allows biolink to correctly construct self-URLs when being served from behind an SSL-terminating proxy (e.g., how it's running behind the GCP load balancer). Without the fix, biolink will assume it's running on HTTP and construct self-URLs with that protocol. Specifically, it looks for a set of headers that your proxy should pass when hitting biolink; more details here: https://werkzeug.palletsprojects.com/en/2.0.x/middleware/proxy_fix/#werkzeug.middleware.proxy_fix.ProxyFix.
Other changes: removed unused imports, reformatted according to PEP8.
Basically, this allows biolink to correctly construct self-URLs when being served from behind an SSL-terminating proxy (e.g., how it's running behind the GCP load balancer). Without the fix, biolink will assume it's running on HTTP and construct self-URLs with that protocol. Specifically, it looks for a set of headers that your proxy should pass when hitting biolink; more details here: https://werkzeug.palletsprojects.com/en/2.0.x/middleware/proxy_fix/#werkzeug.middleware.proxy_fix.ProxyFix.
Other changes: removed unused imports, reformatted according to PEP8.