code: @Override
    public Map<C, V> row(R rowKey) {
      checkNotNull(rowKey);
      Integer rowIndex = rowKeyToIndex.get(rowKey);
      return (rowIndex == null) ? ImmutableMap.<C, V>of() : new Row(rowIndex);
    }
docs: Returns a view of all mappings that have the given row key. If the row key isn't in {@link
  #rowKeySet()}, an empty immutable map is returned.
  
  <p>Otherwise, for each column key in {@link #columnKeySet()}, the returned map associates the
  column key with the corresponding value in the table. Changes to the returned map will update
  the underlying table, and vice versa.
  
  @param rowKey key of row to search for in the table
  @return the corresponding map from column keys to values