In some cases, you don't need to directly manipulate the strings of values in a mime field. But you do need to test if a mime field contains a value (e.g. does the Connection field contain the value "close").
Currently, you must call MIMEField::value_get, but that does a bunch of copies and string allocation which is not needed in our case. We propose adding a MIMEField::value_get_index method which returns the index of the value in the list if it is present and -1 otherwise. Will still need to do the string parsing, but do not need to do the copies and allocation.