function _verifySignature(signature, value) {
        if (value === undefined) {
            console.assert(signature.optional === true, "Missing argument: " + signature.name);
        }
        return true;
    }
Check a parameter value against the given signature
This only checks for optional parameters, not types
Type checking is complex because of $ref and done on the remote end anyways
@param {signature}
@param {value}