Fragment below will write id="element" into the svg

plt.hexbin(x,y, cmap=plt.cm.YlOrRd_r,gid="element")
plt.savefig("img.svg")

which is as we could expect, but

plt.hexbin(x,y, cmap=plt.cm.YlOrRd_r,gid="element",rasterized=True)
plt.savefig("img.svg")

results in <image tag with different id (something like id="image9f9a4ebdcc")

(i am submitting new issue as tcaswell@stackoverflow suggested