Added some more detail to error messages for clarity (see graph_objs.py)
Added some more detail to error messages for clarity (see graph_objs.py)

plotly/plotly.py,plotly/python-api,plotly/plotly.py,ee-in/python-api,plotly/python-api,plotly/plotly.py,ee-in/python-api,ee-in/python-api,plotly/python-api