Daniel-Constantin Mierla writes:
If you want just to check if there is a Refer-To header, you can use the function is_present_hf() from textops module. This is the fastest way to check if a header exists.
this reminds me about the thing that is_present_hf() implementation is not very efficient, because it compares header names as strings. this could be turned into type comparison with aid of a fixup function (for all hfs known to ser).
-- juha