def get_model_agents(self):
        """Return a list of all Agents from all Statements.

        Returns
        -------
        agents : list[indra.statements.Agent]
           A list of Agents that are in the model.
        """
        model_stmts = self.get_statements()
        agents = []
        for stmt in model_stmts:
            for a in stmt.agent_list():
                if a is not None:
                    agents.append(a)
        return agents
Return a list of all Agents from all Statements.

        Returns
        -------
        agents : list[indra.statements.Agent]
           A list of Agents that are in the model.