Scenic.ViewPort.name_to_id

You're seeing just the function name_to_id, go back to Scenic.ViewPort module for more information.
Link to this function

name_to_id(viewport, name)

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Specs

name_to_id(viewport :: t(), name :: any()) ::
  {:ok, non_neg_integer()} | {:error, :not_found}

look up an id for a name. Does not register the name if it is missing