WeChat.sign_jssdk

You're seeing just the function sign_jssdk, go back to WeChat module for more information.

sign_jssdk(jsapi_ticket, url)

sign_jssdk(jsapi_ticket :: String.t(), url :: String.t()) ::
  WeChat.JSSDKSignature.t()

To configure and load WeChat JSSDK in the target page's url properly, use jsapi_ticket and url to generate a signature for this scenario.