Dependency bug

I have just found an issue regarding dependencies of a package... Can I post it as a bug or do I have to write to a forum?
now I'm a bit clearer... The package I'm talking about is matplotlib.. It is a very powerful software to plot graphs and charts through various tools and showing those plots through various backend (GTK+, Qt, etc.).. Since I'm fond of GTK+ and I hate to be stuck to old technologies, I tried to make it work with GTK+ 3 and Python 3 and installed "python3-matplotlib" package together with the suggested dependency suited for GTK3Cairo backend (the only one known to work with the tools I'd like to employ): "python3-cairo".. Things go well until I try to plot a simple function graph... a white canvas on the plotting window.. when I try to move the figure through the toolbox provided by matplotlib, I see a lot of errors appearing on the shell about cairo classes which cannot be found from the gi repository.. So I get the package with the required objects ("python3-gi-cairo").. This seems to have resolved problems with plotting... So shouldn't it be "python3-gi-cairo" the right package to recommend from matplotlib package instead of "python3-cairo"? Besides it depends on both python3-cairo and python3-gi which you require to code with Python3 and GTK+ 3.. I'm sorry if I have been too verbous.. Thanks