Implement generators

[colemathis]

We have at least two different generators we want to explore. These should be implemented in the library.

Each generator should be able to produce N unique lambda expressions.

[colemathis]

This can be done in Python for now. We can just rip https://github.com/AgentElement/lambda-btree and put it in here

[colemathis]

The above code needs to be modified to be able to generate unique expressions for each method.