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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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