function iunmap(keystroke, domain) {
        if (_isDomainApplicable(domain)) {
            insert.mappings.remove(KeyboardUtils.encodeKeystroke(keystroke));
        }
    }
Unmap a key sequence in insert mode.

@param {string} keystroke a key sequence to be removed.
@param {regex} [domain=null] a Javascript regex pattern to identify the domains that this mapping will be removed.

@see unmap