src/main/java/com/arpnetworking/logback/KeyValueEncoder.java
protected String buildFormatString(@Nullable final String name, @Nullable final String[] keys) {
        final String effectiveName = name == null ? _logEventName : name;
        final StringWriter stringWriter = new StringWriter();
        stringWriter.append("name=\"").append(effectiveName).append("\"");
        if (keys != null && keys.length > 0) {
            for (final String key : keys) {
                stringWriter.append(", ").append(key).append("=\"{}\"");
            }
        }
        return stringWriter.toString();
    }
protected String buildFormatString(@Nullable final String name, @Nullable final String[] keys) {
        final String effectiveName = name == null ? _logEventName : name;
        final StringWriter stringWriter = new StringWriter();
        stringWriter.append("name=\"").append(effectiveName).append("\"");
        if (keys != null && keys.length > 0) {
            for (final String key : keys) {
                stringWriter.append(", ").append(key).append("=\"{}\"");
            }
        }
        return stringWriter.toString();
    }
Create a format <code>String</code> compatible with <code>MessageFormatter</code>.

@param name The name.
@param keys The argument keys.
@return The format <code>String</code>.