add example in Figure.append_trace docstring on ref in make_subplots

Author: etpinard

plotly/graph_objs/graph_objs.py

@@ -941,6 +941,17 @@ def append_trace(self, trace, row, col):
         The row, col index is generated from figures created with
         plotly.tools.make_subplots and can be viewed with Figure.print_grid.
 
+        Example:
+        # stack two subplots vertically
+        fig = tools.make_subplots(rows=2)
+
+        This is the format of your plot grid:
+        [ (1,1) x1,y1 ]
+        [ (2,1) x2,y2 ]
+
+        fig.append_trace(Scatter(x=[1,2,3], y=[2,1,2]), 1, 1)
+        fig.append_trace(Scatter(x=[1,2,3], y=[2,1,2]), 2, 1)
+
         Arguments:
 
         trace (plotly trace object):

plotly/tools.py

@@ -511,6 +511,8 @@ def make_subplots(rows=1, cols=1,
     fig['data'] += [Scatter(x=[1,2,3], y=[2,1,2])]
     fig['data'] += [Scatter(x=[1,2,3], y=[2,1,2], xaxis='x2', yaxis='y2')]
 
+    # or see Figure.append_trace
+
     Example 2:
     # subplots with shared x axes
     fig = tools.make_subplots(rows=2, shared_xaxes=True)