[SIP Beyond VoIP] Question about header field 'Supported' when using session.connect

[Goran Lazaroski]

Hello,
 
I am new to this.
I have a question about using the session.connect method(for example in the SipSessionExample).
When calling this method there is always a header field 'Supported' with several options like '100rel','replaces' etc.
Where are these values coming from?
Is there a way to change this values? I want to replace this settings with for example 'Supported':'timer'.
I have used the 'extra_header' in the session.connect method but it generates a second 'Supported' field with the new values and not replacing the old one.
 
I am using Python.
 
For further information ask me please.
 
Best regards
Go14