Parent and child conflict

[algomaster99]

We assume that module under modules are children. However, the parent module can also declare its child as a parent. For example, consider bnd@6.3.0:

bnd-plugin-parent is declared as a parent and child so it is not straightforward to construct a graph. I also checked that bnd-plugin-parent would not be where the root pom is as it does not have any modules.