Add id attribute to data api xml output

metobsapi/modifyData.py

@@ -187,8 +187,9 @@ def handle_xml(frame, symbols, epoch, sep=',', **kwargs):
     head.appendChild(columns_elem)
 
     data_elem = doc.createElement('data')
-    for t, row in frame.iterrows():
+    for idx, (t, row) in enumerate(frame.iterrows()):
         row_elem = doc.createElement('row')
+        row_elem.setAttribute('id', str(idx))
         row_elem.appendChild(doc.createTextNode(str(t)))
         for point in row:
             row_elem.appendChild(doc.createTextNode(str(point)))