code: public int spanBack(CharSequence s, SpanCondition spanCondition) {
          return spanBack(s, s.length(), spanCondition);
      }
docs: Span a string backwards (from the end) using this UnicodeSet.
  <p>To replace, count elements, or delete spans, see {@link android.icu.text.UnicodeSetSpanner UnicodeSetSpanner}.
  @param s The string to be spanned
  @param spanCondition The span condition
  @return The string index which starts the span (i.e. inclusive).