'Increment the value of C{key} by given value (default to 1).
C{key} must be consistent with an int. Return the new value.
@param key: the key to modify.
@type key: L{bytes}
@param val: the value to increment.
@type val: L{int}
@return: a deferred with will be called back with the new value
associated with the key (after the increment).
@rtype: L{Deferred}'

def increment(self, key, val=1):

    return self._incrdecr('incr', key, val)
