code: public static String delete(final String str, final String... set) {
          if (StringUtils.isEmpty(str) || deepEmpty(set)) {
              return str;
          }
          return modify(str, set, false);
      }
docs: <p>Takes an argument in set-syntax, see evaluateSet,
  and deletes any of characters present in the specified string.</p>
  
  <pre>
  CharSetUtils.delete(null, *)        = null
  CharSetUtils.delete("", *)          = ""
  CharSetUtils.delete(*, null)        = *
  CharSetUtils.delete(*, "")          = *
  CharSetUtils.delete("hello", "hl")  = "eo"
  CharSetUtils.delete("hello", "le")  = "ho"
  </pre>
  
  @see CharSet#getInstance(java.lang.String...) for set-syntax.
  @param str  String to delete characters from, may be null
  @param set  String[] set of characters to delete, may be null
  @return the modified String, {@code null} if null string input