code: def transfer(self, receiver_address, amount, sender_account):
          
          self._keeper.token.token_approve(receiver_address, amount,
                                           sender_account)
          self._keeper.token.transfer(receiver_address, amount, sender_account)
docs: 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