def incrby(
        self,
        fmt: str,
        offset: BitfieldOffsetT,
        increment: int,
        overflow: Optional[str] = None,
    ):
        """
        Increment a bitfield by a given amount.
        :param fmt: format-string for the bitfield being updated, e.g. 'u8'
            for an unsigned 8-bit integer.
        :param offset: offset (in number of bits). If prefixed with a
            '#', this is an offset multiplier, e.g. given the arguments
            fmt='u8', offset='#2', the offset will be 16.
        :param int increment: value to increment the bitfield by.
        :param str overflow: overflow algorithm. Defaults to WRAP, but other
            acceptable values are SAT and FAIL. See the Redis docs for
            descriptions of these algorithms.
        :returns: a :py:class:`BitFieldOperation` instance.
        """
        if overflow is not None:
            self.overflow(overflow)

        self.operations.append(("INCRBY", fmt, offset, increment))
        return self

        Increment a bitfield by a given amount.
        :param fmt: format-string for the bitfield being updated, e.g. 'u8'
            for an unsigned 8-bit integer.
        :param offset: offset (in number of bits). If prefixed with a
            '#', this is an offset multiplier, e.g. given the arguments
            fmt='u8', offset='#2', the offset will be 16.
        :param int increment: value to increment the bitfield by.
        :param str overflow: overflow algorithm. Defaults to WRAP, but other
            acceptable values are SAT and FAIL. See the Redis docs for
            descriptions of these algorithms.
        :returns: a :py:class:`BitFieldOperation` instance.
        
aioredis/client.py