def METHOD_NAME(self):
    """
    A graph operation which purges everything in the graph except for the
    drivers still in processing status.
    """
    self.vertices = {d: self.vertices[d] for d in self.processing}
    self.edges = {d: dict() for d in self.vertices}
    self.indegrees = {d: 0 for d in self.vertices}
    self.outdegrees = {d: 0 for d in self.vertices}