[galaxy-dev] tool_dependencies inside tool_dependencies

Hi, is there a general rule to handle dependencies inside of tool_dependencies.xml? Lets assume I write a matplotlib orphan tool_dependencies.xml file. matplotlib depends on numpy. Numpy has already a orphan definition. Is there a way to include numpy as dependency inside the matplotlib-definition, so that I did not need to fetch and compile numpy inside of matplotlib? I tried to specify it beforehand but that did not work. Thanks! Bjoern