Returns a list of pairs of account and block hash representing the
        head block for **accounts** list

        :param accounts: Accounts to return frontier blocks for
        :type accounts: list of str

        :raises: :py:exc:`nano.rpc.RPCException`

        >>> rpc.accounts_frontiers(
        ...     accounts=[
        ...         "xrb_3t6k35gi95xu6tergt6p69ck76ogmitsa8mnijtpxm9fkcm736xtoncuohr3",
        ...         "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7"
        ...     ]
        ... )
        {
            "xrb_3t6k35gi95xu6tergt6p69ck76ogmitsa8mnijtpxm9fkcm736xtoncuohr3":
                "791AF413173EEE674A6FCF633B5DFC0F3C33F397F0DA08E987D9E0741D40D81A",
            "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7":
                "6A32397F4E95AF025DE29D9BF1ACE864D5404362258E06489FABDBA9DCCC046F"
        }

def accounts_frontiers(self, accounts):
        """
        Returns a list of pairs of account and block hash representing the
        head block for **accounts** list

        :param accounts: Accounts to return frontier blocks for
        :type accounts: list of str

        :raises: :py:exc:`nano.rpc.RPCException`

        >>> rpc.accounts_frontiers(
        ...     accounts=[
        ...         "xrb_3t6k35gi95xu6tergt6p69ck76ogmitsa8mnijtpxm9fkcm736xtoncuohr3",
        ...         "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7"
        ...     ]
        ... )
        {
            "xrb_3t6k35gi95xu6tergt6p69ck76ogmitsa8mnijtpxm9fkcm736xtoncuohr3":
                "791AF413173EEE674A6FCF633B5DFC0F3C33F397F0DA08E987D9E0741D40D81A",
            "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7":
                "6A32397F4E95AF025DE29D9BF1ACE864D5404362258E06489FABDBA9DCCC046F"
        }

        """

        accounts = self._process_value(accounts, 'list')

        payload = {"accounts": accounts}

        resp = self.call('accounts_frontiers', payload)

        return resp.get('frontiers') or {}