static Appendable indent(final Appendable appendable, final int level) throws IOException
    {
        Appendable out = appendable;
        for (int i = 0; i < level; i++)
        {
            out = out.append(INDENT);
        }

        return out;
    }
Converts to 'snake_case' but will also handle when there are multiple
upper case characters in a row 'UPPERCase' => 'upper_case'.

@param value to be formatted
@return the string formatted to 'lower_snake_case'
sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/rust/RustUtil.java