code: private IndexExpression indexedExpression(List<IndexExpression> clause) {
          for (IndexExpression indexExpression : clause) {
              ByteBuffer columnName = indexExpression.column;
              if (indexedColumnName.equals(columnName)) {
                  return indexExpression;
              }
          }
          return null;
      }
docs: Returns the {@link IndexExpression} relative to this index.
  
  @param clause A list of {@link IndexExpression}s.
  @return The {@link IndexExpression} relative to this index.