DBConnection.handle_status

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

handle_status(opts, state)

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Specs

handle_status(opts :: Keyword.t(), state :: any()) ::
  {status(), new_state :: any()}
  | {:disconnect, Exception.t(), new_state :: any()}

Handle getting the transaction status. Return {:idle, state} if outside a transaction, {:transaction, state} if inside a transaction, {:error, state} if inside an aborted transaction, or {:disconnect, exception, state} to error and disconnect.

If the callback returns a :disconnect tuples then status/2 will return :error.