If encoders aren't relevant, raise NotEncodable instead of returning None
If encoders aren't relevant, raise NotEncodable instead of returning None

Returning None for encoders failed in the case where the encodable value
was actually None, like pd.NaT -> None

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