code: public Long getLong(String nameSpace, String cellName) {
          return getValue(nameSpace, cellName, Long.class);
      }
docs: Returns the {@code Long} value of the {@link Cell} (associated to {@code table}) whose name iscellName, or null
  if this Cells object contains no cell whose name is cellName.
  
  @param nameSpace the name of the owning table
  @param cellName  the name of the Cell we want to retrieve from this Cells object.
  @return the {@code Long} value of the {@link Cell} (associated to {@code table}) whose name is cellName, or null
  if this Cells object contains no cell whose name is cellName