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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 push_power_button(self, target_value):
 """Reset the system in hpe exclusive manner. :param target_value: The target value to be set. :raises: InvalidInputError, if the target value is not allowed. :raises: SushyError, on an error from iLO. """

        if target_value not in mappings.PUSH_POWER_BUTTON_VALUE_MAP_REV:
            msg = ('The parameter "%(parameter)s" value "%(target_value)s" is '
                   'invalid. Valid values are: %(valid_power_values)s' %
                   {'parameter': 'target_value', 'target_value': target_value,
                    'valid_power_values': (
                        mappings.PUSH_POWER_BUTTON_VALUE_MAP_REV.keys())})
            raise exception.InvalidInputError(msg)

        value = mappings.PUSH_POWER_BUTTON_VALUE_MAP_REV[target_value]
        target_uri = (
            self._get_hpe_push_power_button_action_element().target_uri)

        self._conn.post(target_uri, data={'PushType': value})