function Contour(params) {
    Transform.call(this, null, params);
  }
Generate contours based on kernel-density estimation of point data.
@constructor
@param {object} params - The parameters for this operator.
@param {Array<number>} params.size - The dimensions [width, height] over which to compute contours.
 If the values parameter is provided, this must be the dimensions of the input data.
 If density estimation is performed, this is the output view dimensions in pixels.
@param {Array<number>} [params.values] - An array of numeric values representing an
 width x height grid of values over which to compute contours. If unspecified, this
 transform will instead attempt to compute contours for the kernel density estimate
 using values drawn from data tuples in the input pulse.
@param {function(object): number} [params.x] - The pixel x-coordinate accessor for density estimation.
@param {function(object): number} [params.y] - The pixel y-coordinate accessor for density estimation.
@param {function(object): number} [params.weight] - The data point weight accessor for density estimation.
@param {number} [params.cellSize] - Contour density calculation cell size.
@param {number} [params.bandwidth] - Kernel density estimation bandwidth.
@param {Array<number>} [params.thresholds] - Contour threshold array. If
  this parameter is set, the count and nice parameters will be ignored.
@param {number} [params.count] - The desired number of contours.
@param {boolean} [params.nice] - Boolean flag indicating if the contour
  threshold values should be automatically aligned to "nice"
  human-friendly values. Setting this flag may cause the number of
  thresholds to deviate from the specified count.
@param {boolean} [params.smooth] - Boolean flag indicating if the contour
  polygons should be smoothed using linear interpolation. The default is
  true. The parameter is ignored when using density estimation.