code: public static CharSequence subSequence(final CharSequence cs, final int start) {
          return cs == null ? null : cs.subSequence(start, cs.length());
      }
docs: <p>Returns a new {@code CharSequence} that is a subsequence of this
  sequence starting with the {@code char} value at the specified index.</p>
  
  <p>This provides the {@code CharSequence} equivalent to {@link String#substring(int)}.
  The length (in {@code char}) of the returned sequence is {@code length() - start},
  so if {@code start == end} then an empty sequence is returned.</p>
  
  @param cs  the specified subsequence, null returns null
  @param start  the start index, inclusive, valid
  @return a new subsequence, may be null
  @throws IndexOutOfBoundsException if {@code start} is negative or if
  {@code start} is greater than {@code length()}