:param project_id: UUID of the project
        :returns: a free dynamips id

def get_dynamips_id(self, project_id):
        """
        :param project_id: UUID of the project
        :returns: a free dynamips id
        """
        self._dynamips_ids.setdefault(project_id, set())
        for dynamips_id in range(1, 4097):
            if dynamips_id not in self._dynamips_ids[project_id]:
                self._dynamips_ids[project_id].add(dynamips_id)
                return dynamips_id
        raise DynamipsError("Maximum number of Dynamips instances reached")