diff --git a/src/backends.jl b/src/backends.jl
index 1d4b3482..9bf596fd 100644
--- a/src/backends.jl
+++ b/src/backends.jl
@@ -707,7 +707,7 @@ const _pgfplotsx_attr = merge_with_base_supported([
 ])
 const _pgfplotsx_seriestype =
         [:path,  :scatter, :straightline,
-        :path3d, :scatter3d, :surface, :wireframe, :volume,
+        :path3d, :scatter3d, :surface, :wireframe, 
         :heatmap, :contour, :histogram2d,
         :shape,
         :steppre, :stepmid, :steppost,  :ysticks, :xsticks]
diff --git a/src/backends/pgfplotsx.jl b/src/backends/pgfplotsx.jl
index e3441d0b..c7a3889b 100644
--- a/src/backends/pgfplotsx.jl
+++ b/src/backends/pgfplotsx.jl
@@ -37,7 +37,6 @@ function Base.push!(pgfx_plot::PGFPlotsXPlot, item)
 end
 
 function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
-    # TODO: annotations! does not trigger _series_added ...
     if !pgfx_plot.is_created
         cols, rows = size(plt.layout.grid)
         the_plot = PGFPlotsX.TikzPicture()
@@ -126,7 +125,6 @@ function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
                 push!( axis_opt, "view" => (azim, elev) )
             end
             axisf = if sp[:projection] == :polar
-                        # TODO: this errors for some reason
                         # push!(axis_opt, "xmin" => 90)
                         # push!(axis_opt, "xmax" => 450)
                         PGFPlotsX.PolarAxis
@@ -194,14 +192,6 @@ function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
                                 "labels" => opt[:contour_labels],
                             )
                         )
-                        else
-                            notimpl()
-                            push!(series_opt,
-                                "contour filled" => PGFPlotsX.Options(
-                                    # "levels" => opt[:levels],
-                                    # "labels" => opt[:contour_labels],
-                                )
-                            )
                         end
                     end
                     coordinates = pgfx_series_coordinates!( sp, st, segment_opt, opt, rng )
@@ -390,7 +380,6 @@ const _pgfx_annotation_halign = KW(
 )
 ## --------------------------------------------------------------------------------------
 # Generates a colormap for pgfplots based on a ColorGradient
-# TODO: maybe obsolete
 pgfx_arrow(::Nothing) = "every arrow/.append style={-}"
 function pgfx_arrow( arr::Arrow )
     components = String[]
diff --git a/test/test_pgfplotsx.jl b/test/test_pgfplotsx.jl
index 70f51a72..4192e354 100644
--- a/test/test_pgfplotsx.jl
+++ b/test/test_pgfplotsx.jl
@@ -70,11 +70,9 @@ end
          x = 0.1:0.2:0.9
          y = 0.7 * rand(5) .+ 0.15
          plot(x, y, line=(3, :dash, :lightblue), marker=(Shape(verts), 30, RGBA(0, 0, 0, 0.2)), bg=:pink, fg=:darkblue, xlim=(0, 1), ylim=(0, 1), leg=false)
-         # TODO: draw those polygons
      end # testset
      @testset "Histogram 2D" begin
         histogram2d(randn(10000), randn(10000), nbins=20)
-        # TODO: should work, when heatmaps works?
      end # testset
      @testset "Heatmap-like" begin
         xs = [string("x", i) for i = 1:10]
@@ -102,7 +100,6 @@ end
         p2 = contour(x, y, Z)
         p1 = contour(x, y, f, fill=true)
         plot(p1, p2)
-        # TODO: filled contours
      end # testset
      @testset "Varying colors" begin
         t = range(0, stop=1, length=100)