The part's root element, cx:chartSpace.
Whether the workbook behind the chart counts dates from 1904.
Optional Readonlydate1904?: booleanDefault false.
The chart, as the Excel adapter converts it; null when the part
is not a chart. A layout MAIDR does not know reads as Invalid, so the
converter says it cannot read it.
Read a chart part of a type Office 2016 added.