code: public long term(long index) {
      assertIsOpen();
      assertValidIndex(index);
  
      Segment segment = segments.segment(index);
      Assert.index(segment != null, "invalid index: " + index);
  
      return segment.term(index);
    }
docs: Returns the term for the entry at the given index.
  <p>
  This method provides a more efficient means of reading an entry term without deserializing the entire entry.
  Servers should use this method when performing consistency checks that don't require reading the full entry
  object. Terms can typically be read in O(1) time with no disk access on segments that haven't been compacted.
  <p>
  If the given index is outside of the bounds of the log then a {@link IndexOutOfBoundsException} will be thrown. If
  the entry at the given index has been compacted then the returned entry will be {@code null}.
  
  @param index The index for which to return the term.
  @return The term for the entry at the given index.