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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 transfer(self, receiver_address, amount, sender_account):
 """ Transfer a number of tokens from `sender_account` to `receiver_address` :param receiver_address: hex str ethereum address to receive this transfer of tokens :param amount: int number of tokens to transfer :param sender_account: Account instance to take the tokens from :return: bool """

        self._keeper.token.token_approve(receiver_address, amount,
                                         sender_account)
        self._keeper.token.transfer(receiver_address, amount, sender_account)