code: public String rowPut(String key, RowSpec value) {
          return rowPut(key, value.encode());
      }
docs: Associates the specified ColumnSpec with the specified key in this map. If the map previously
  contained a mapping for this key, the old value is replaced by the specified value. The
  RowSpec set in this map override an association - if any - in the chain of parent
  LayoutMaps.<p>
  
  The RowSpec must not be {@code null}. To remove an association from this map use
  {@link #rowRemove(String)}.
  
  @param key key with which the specified value is to be associated.
  @param value ColumnSpec to be associated with the specified key.
  @return previous ColumnSpec associated with specified key, or {@code null} if there was no
  mapping for key.
  
  @throws NullPointerException if the {@code key} or {@code value} is {@code null}.
  
  @see Map#put(Object, Object)