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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 policy(self, observations):
 """ Calculate only action head for given state """

        input_data = self.input_block(observations)
        policy_base_output = self.policy_backbone(input_data)
        policy_params = self.action_head(policy_base_output)
        return policy_params