Allow setting zmid with zmin and zmax in plotly.graph_objects.Heatmap

Feature request

I've been trying to plot a subset of a ranked list (gene differential expression dataset). I would like the minimum and maximum color scale set to that of the original complete ranked list, with the midpoint set to zero. It currently seems to be impossible in plotly to do this. I can plot the subset with the colorscale min and max set to the original dataset min and max, but this causes the midpoint to no longer be set to zero.

It can be desirable to set a colorscale to the minimum and maximum of a positive/negative spanned dateset with unequal absolutes but to still have the midpoint at zero without needing to construct and entirely custom colorscale. zmid being ignored when zmax and zmin are set just seems a super odd behavior to me.

Comienza en plotly.graph_objects.Heatmap y sigue cómo se gestionan zmin, zmax y zmid para la escala de colores. Revisa las pruebas existentes de Heatmap en busca de comportamientos relacionados. Se considerará terminado cuando zmid siga siendo efectivo aunque zmin y zmax estén establecidos explícitamente, con cobertura para límites positivos y negativos desiguales.