code: public static String unwrap(final String str, final String wrapToken) {
          if (isEmpty(str) || isEmpty(wrapToken)) {
              return str;
          }
  
          if (startsWith(str, wrapToken) && endsWith(str, wrapToken)) {
              final int startIndex = str.indexOf(wrapToken);
              final int endIndex = str.lastIndexOf(wrapToken);
              final int wrapLength = wrapToken.length();
              if (startIndex != -1 && endIndex != -1) {
                  return str.substring(startIndex + wrapLength, endIndex);
              }
          }
  
          return str;
      }
docs: <p>
  Unwraps a given string from anther string.
  </p>
  
  <pre>
  StringUtils.unwrap(null, null)         = null
  StringUtils.unwrap(null, "")           = null
  StringUtils.unwrap(null, "1")          = null
  StringUtils.unwrap("\'abc\'", "\'")    = "abc"
  StringUtils.unwrap("\"abc\"", "\"")    = "abc"
  StringUtils.unwrap("AABabcBAA", "AA")  = "BabcB"
  StringUtils.unwrap("A", "#")           = "A"
  StringUtils.unwrap("#A", "#")          = "#A"
  StringUtils.unwrap("A#", "#")          = "A#"
  </pre>
  
  @param str
  the String to be unwrapped, can be null
  @param wrapToken
  the String used to unwrap
  @return unwrapped String or the original string
  if it is not quoted properly with the wrapToken
  @since 3.6