Memory caching with GraphPipeline may miss some nodes where the ordering on inputs happens to be different between two nodes. - potential solution is to make graphs canonical - there is a C package that can be imported into TPOT that may do this

[perib]

This should be rare. The order of inputs is determined alphabetically. For this to be an issue we would have to have two modules of the same type, each with different inputs, whos output goes to the same node.

related to #73