Sippet.Message.update_header_back

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update_header_back(message, header, initial \\ nil, fun)

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Specs

update_header_back(
  t(),
  header(),
  value() | nil,
  (multiple_value() -> multiple_value())
) :: t()

Updates the last header value in message with the given function.

If header is present in message with value [value], fun is invoked with for last element of [value] and its result is used as the new value of header back. If header is not present in message, or it is an empty list, initial is inserted as the single value of header.