docs: private void generateExtensionCheck(
          final StringBuilder sb,
          final char varName)
      {
          this.imports.add("io");
          this.imports.add("io/ioutil");
          sb.append(String.format(
              "\tif actingVersion > %1$s.SbeSchemaVersion() && blockLength > %1$s.SbeBlockLength() {\n" +
              "\t\tio.CopyN(ioutil.Discard, _r, int64(blockLength-%1$s.SbeBlockLength()))\n" +
              "\t}\n",
              varName));
      }