im mpl_fig.py: add comments

    to clarify the fact that set_rawdata is not part of the public API. use `update(rawdata=...)` instead.

mpl_fig.py

@@ -872,9 +872,16 @@ class MplFig(metaclass=FigureClassFactory, context=CONTEXT.lower()):
         in a similar way as a local figure would do.
         Warning : No consitancy checking is done. The server 
         side will report the errors.
+
+        Do not call directly: to change rawdata call:
+
+            fig.update(rawdata=...)
+
         '''
         self.remote_rawdata = rawdata
         self.formatted = False
+        # WARNING: in client context doe not call set_rawdata!!!
+        # self.update(rawdata=rawdata) <-- this calls set_rawdata... 
 
     def _format_rawdata_client(self):
         """ send a signal to the server