"None" value of `hovertext` is shown as String

[pmercatoris]

In plotly 2.5.1, a None value of hovertext would result in the hoverinfo being skipped.
However, in 3.3.0, that is not the case. Instead, it will show the None as a string.

import plotly.graph_objs as go

test = go.Scatter(
    x=[0,1],
    y=[0,1],
    hovertext=[None, 'test'],
    mode='lines',
    hoverinfo='x+text',
)

In 2.5.1, test is:

{'hoverinfo': 'x+text',
 'hovertext': [None, 'test'],
 'mode': 'lines',
 'type': 'scatter',
 'x': [0, 1],
 'y': [0, 1]}

In 3.3.0, test is:

Scatter({
    'hoverinfo': 'x+text', 'hovertext': ['None', 'test'], 'mode': 'lines', 'x': [0, 1], 'y': [0, 1]
})

Resulting in this:

[jonmmease]

Thanks for the report @pmercatoris, I see what you mean. It looks like we're inadvertently converting None values to strings during validation.

[jonmmease]

Done in #1249 and will be released in version 3.4.0. Thanks for taking the time to let us know!