Build a hierarchy from a relational data-set using Pyspark

I am new to Python and stuck with building a hierarchy out of a relational dataset.
It would be of immense help if someone has an idea on how to proceed with this.

I have a relational data-set with data like

_currentnode,  childnode_   root,         child1   child1,       leaf2   child1,       child3   child1,       leaf4   child3,       leaf5   child3,       leaf6  

so-on. I am looking for some python or pyspark code to
build a hierarchy dataframe like below

_level1, level2,  level3,  level4_  root,    child1,  leaf2,   null  root,    child1,  child3,  leaf5  root,    child1,  child3,  leaf6  root,    child1,  leaf4,   null  

The data is alpha-numerics and is a huge dataset[~50mil records].
Also, the root of the hierarchy is known and can be hardwired in the code.
So in the example, above, the root of the hierarchy is 'root'.