Requiem.handle_stream

You're seeing just the callback handle_stream, go back to Requiem module for more information.
Link to this callback

handle_stream(stream_id, data, conn, state)

Specs

handle_stream(
  stream_id :: non_neg_integer(),
  data :: binary(),
  conn :: Requiem.ConnectionState.t(),
  state :: any()
) ::
  {:ok, Requiem.ConnectionState.t(), any()}
  | {:ok, Requiem.ConnectionState.t(), any(), timeout() | :hibernate}
  | {:stop, non_neg_integer(), atom()}