FileStorageApi.File.public_url

You're seeing just the function public_url, go back to FileStorageApi.File module for more information.
Link to this function

public_url(container_name, file_path, start_time \\ Timex.now(), expire_time \\ Timex.add(Timex.now(), Timex.Duration.from_days(1)))

Specs

public_url(String.t(), String.t(), DateTime.t(), DateTime.t()) ::
  {:ok, String.t()} | {:error, String.t()}

public_url returns an full url to be able to fetch the file with security tokens needed by default 1 day valid