parameters: (self, opt)
return_statement: return opt.lower() in self.esmtp_features
docstring: Does the server support a given SMTP service extension?
docstring_summary: Does the server support a given SMTP service extension?
docstring_tokens: Does the server support a given SMTP service extension?
function: def has_extn(self, opt):
          """Does the server support a given SMTP service extension?"""
          return opt.lower() in self.esmtp_features
function_tokens: def has_extn ( self , opt ) : return opt . lower ( ) in self . esmtp_features