def __call__(self, start, end):
assert len( list(self.nodes.keys()) ) > <NUM_LIT:0>, "<STR_LIT>"<EOL>cmp_sequence = list(zip( self.nodes[start], self.nodes[end] ))<EOL>chow_number = max( abs( a-b ) for a,b in cmp_sequence )<EOL>return chow_number<EOL>
Estimate how far start is from end.

@type  start: node
@param start: Start node.

@type  end: node
@param end: End node.