code: def node_to_hdd(node):
      
      if not len(node):
          return None
      hdds = []
      for subnode in node.nodes:
          if not all([subnode.attrib[key] for key in ["depth", "probability"]]):
              return None
          hdds.append((float(subnode.attrib["probability"]),
                       float(subnode.attrib["depth"])))
      return PMF(hdds)
docs: Parses the node to a hpyocentral depth distribution PMF