Accept any dateformatter! 'DateFormatter' is always in the string.
Accept any dateformatter! 'DateFormatter' is always in the string.

There might be a super class we could test the instance of, but
this is easy enough for now.

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