code: def create_signature(self, name, content, contenttype="text/html"):
          
          s = zobjects.Signature(name=name)
          s.set_content(content, contenttype)
  
          resp = self.request('CreateSignature', {'signature': s.to_creator()})
          return zobjects.Signature.from_dict(resp['signature'])
docs: :param:  name        verbose name of the signature
          :param:  content     content of the signature, in html or plain-text
          :param:  contenttype can be "text/html" (default) or "text/plain"
          :returns: a zobjects.Signature object