Orientation of y-axis in Heatmap

The default orientation of the y-axis in the Heatmap graph is, at least to me, unexpected. The 0,0 coordinate of the plot is in the lower left corner. A heatmap is generally used to display a matrix, such as an image, however, and the 0,0 index into the matrix would be in the top left corner. An image is thus displayed flipped upside down. One can of course flip the z array or provide the values for y in reversed order, but this keeps the labelling of the axis and the display of y,x in the hover window unaffected. I like the way this is handled in matplotlib.pyplot.imshow, which provides an origin argument.
An additional argument for the Heatmap graph to control the orientation of the y-axis would be nice.

Start at the Heatmap graph entry point and inspect how its y-axis and hover labels are handled; compare the requested behavior with matplotlib.pyplot.imshow's origin argument. Done means an optional orientation argument controls the displayed y direction while axis labels and hover coordinates remain consistent, with coverage for both orientations.