Create a new node type that wraps pzflow and create an introductory notebook

[jeremykubica]

Create a new node type that allows us to consistently sample from pzflow. This node will determine its parameters based on the information the flow computes, allowing them to be used for other parameter setters.

The demo notebook includes the basics of setting up nodes and sampling. It uses the new pzflow node as an example.

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Before [9ea64af]	After [1a7bf09]	Ratio	Benchmark (Parameter)
1.33±0.01s	1.38±0.01s	1.04	benchmarks.TimeSuite.time_make_x1_from_hostmass
4.31±0.1ms	4.44±1ms	1.03	benchmarks.TimeSuite.time_chained_evaluate
700±700μs	719±20μs	1.03	benchmarks.TimeSuite.time_fnu_to_flam
4.68±0.1ms	4.71±0.1ms	1.01	benchmarks.TimeSuite.time_evaluate_salt3_passbands
8.90±0.03ms	8.95±0.08ms	1.01	benchmarks.TimeSuite.time_load_passbands
122±0.8μs	122±2μs	1	benchmarks.TimeSuite.time_sample_x0_from_distmod
8.55±0.7ms	8.47±0.3ms	0.99	benchmarks.TimeSuite.time_evaluate_salt3_model
16.1±0.1μs	15.9±0.2μs	0.99	benchmarks.TimeSuite.time_sample_x1_from_hostmass
27.7±0.2μs	27.2±0.3μs	0.98	benchmarks.TimeSuite.time_make_new_salt3_model
1.46±0.08ms	1.38±0.06ms	0.94	benchmarks.TimeSuite.time_apply_passbands

Click here to view all benchmarks.