You're seeing just the function read_values, go back to Circuits.GPIO.Chip module for more information.
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read_values(Circuits.GPIO.Chip.LineHandle.t()) ::
  {:ok, [offset_value()]} | {:error, atom()}

Read values for a line handle

This is useful when you a line handle that contains multiple GPIO offsets.

{:ok, line_handle} = Circuits.GPIO.Chip.request_lines("gpiochip0", [17, 22, 23, 24])
{:ok, [0, 0, 0, 0]} = Circuits.GPIO.Chip.read_values(line_handle)

Note that the values in the list match the index order of how the offsets were requested.

Note that the order of the values returned return the order that the offsets were requested.