Determines whether or not the contour level attributes are picked by an algorithm. If *true*, the number of contour levels can be set in `ncontours`. If *false*, set the contour level attributes in `contours`.

Sets the maximum number of contour levels. The actual number of contours will be chosen automatically to be less than or equal to the value of `ncontours`. Has an effect only if `autocontour` is *true* or if `contours.size` is missing.

If `levels`, the data is represented as a contour plot with multiple levels displayed. If `constraint`, the data is represented as constraints with the invalid region shaded as specified by the `operation` and `value` parameters.

Sets the starting contour level value. Must be less than `contours.end`

Sets the end contour level value. Must be more than `contours.start`

Sets the step between each contour level. Must be positive.

Determines the coloring method showing the contour values. If *fill*, coloring is done evenly between each contour level If *heatmap*, a heatmap gradient coloring is applied between each contour level. If *lines*, coloring is done on the contour lines. If *none*, no coloring is applied on this trace.

Determines whether or not the contour lines are drawn. Has an effect only if `contours.coloring` is set to *fill*.

Determines whether to label the contour lines with their values.

Sets the font used for labeling the contour levels. The default color comes from the lines, if shown. The default family and size come from `layout.font`.

Sets the contour label formatting rule using d3 formatting mini-language which is very similar to Python, see: https://github.com/d3/d3-3.x-api-reference/blob/master/Formatting.md#d3_format

Sets the constraint operation. *=* keeps regions equal to `value` *<* and *<=* keep regions less than `value` *>* and *>=* keep regions greater than `value` *[]*, *()*, *[)*, and *(]* keep regions inside `value[0]` to `value[1]` *][*, *)(*, *](*, *)[* keep regions outside `value[0]` to value[1]` Open vs. closed intervals make no difference to constraint display, but all versions are allowed for consistency with filter transforms.