: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

def create_signature(self, name, content, contenttype="text/html"):
        """
        :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
        """
        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'])