"""Evaluate a Graph of Nodes."""
from __future__ import print_function
__all__ = ['Engine']


class Engine(object):
    """Evaluate a Graph of Nodes."""

    @staticmethod
    def evaluate_entire_graph(graph):
        """Evaluate the dirty nodes in the graph."""
        for node in graph.evaluation_sequence:
            node.evaluate()
    # end def evaluate_entire_graph

    @staticmethod
    def evaluate_dirty_nodes(graph):
        """Evaluate the dirty nodes in the graph."""
        dirty_nodes = graph.dirty_nodes
        while dirty_nodes:
            for node in dirty_nodes:
                node.evaluate()
            dirty_nodes = graph.dirty_nodes
    # end def evaluate_dirty_nodes
# end class Engine

@@ -480,37 +480,35 @@
 %22%22%22%0A        
-dirty_
+for 
 node
-s =
+ in
  graph.dirty
@@ -517,148 +517,37 @@
 odes
-%0A        while dirty_nodes:%0A            for node in dirty_nodes:%0A                node.evaluate()%0A            dirty_nodes = graph.dirty_nodes
+:%0A            node.evaluate()
 %0A   

Update engine.py