Returns operation name.
           action -- soapAction value

def getOperationName(self, ps, action):
        '''Returns operation name.
           action -- soapAction value
        '''
        method = self.root.get(_get_element_nsuri_name(ps.body_root)) or \
            self.soapAction.get(action)
        if method is None:
            raise UnknownRequestException, \
                'failed to map request to a method: action(%s), root%s' %(action,_get_element_nsuri_name(ps.body_root))
        return method