docs: def incrby(self, key, increment):
          """Increments the number stored at key by increment. If the key does
          not exist, it is set to 0 before performing the operation. An error is
          returned if the key contains a value of the wrong type or contains a
          string that can not be represented as integer. This operation is
          limited to 64 bit signed integers.
  
          See :meth:`~tredis.RedisClient.incr` for extra information on
          increment/decrement operations.
  
          .. versionadded:: 0.2.0
  
          .. note:: **Time complexity**: ``O(1)``
  
          :param key: The key to increment
          :type key: :class:`str`, :class:`bytes`
          :param int increment: The amount to increment by
          :returns: The value of key after the increment
          :rtype: int
          :raises: :exc:`~tredis.exceptions.RedisError`
  
          """
          return self._execute([b'INCRBY', key, ascii(increment)])