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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 add_policy_statements(self, statements):
 """Adds statements to the policy. Args: statements (:class:`awacs.aws.Statement` or list):
 Either a single Statment, or a list of statements. """

        if isinstance(statements, Statement):
            statements = [statements]
        self._policy_statements.extend(statements)