docs: function parse_cs_xml(data/*:?string*/, opts, idx/*:number*/, rels, wb/*::, themes, styles*/)/*:Worksheet*/ {
  	if(!data) return data;
  	/* 18.3.1.12 chartsheet CT_ChartSheet */
  	if(!rels) rels = {'!id':{}};
  	var s = {'!type':"chart", '!chart':null, '!rel':""};
  	var m;
  
  	/* 18.3.1.83 sheetPr CT_ChartsheetPr */
  	var sheetPr = data.match(sheetprregex);
  	if(sheetPr) parse_ws_xml_sheetpr(sheetPr[0], s, wb, idx);
  
  	/* 18.3.1.36 drawing CT_Drawing */
  	if((m = data.match(/drawing r:id="(.*?)"/))) s['!rel'] = m[1];
  
  	if(rels['!id'][s['!rel']]) s['!chart'] = rels['!id'][s['!rel']];
  	return s;
  }