SlackNotification.head

You're seeing just the function head, go back to SlackNotification module for more information.
Link to this function

head(client, url, opts)

Specs

Perform a HEAD request.

See request/1 or request/2 for options definition.

head("/users")
head("/users", query: [scope: "admin"])
head(client, "/users")
head(client, "/users", query: [scope: "admin"])