Mint.HTTP.get_proxy_headers

You're seeing just the function get_proxy_headers, go back to Mint.HTTP module for more information.
Link to this function

get_proxy_headers(conn)

View Source (since 1.4.0)

Specs

get_proxy_headers(t()) :: Mint.Types.headers()

Gets the proxy headers associated with the connection in the CONNECT method.

When using tunnel proxy and HTTPs, the only way to exchange data with the proxy is through headers in the CONNECT method.