Add Notebook for Loading Data to NestedPandas

[wilsonbb]

Change Description

Adds a tutorial notebook to demonstrate data loading for NestedPandas (from a dictionary or from parquet file(s)). Also demonstrates than an existed NestedFrame can be saved to either a single parquet file or to multiple parquet files (one for each layer).

Addresses #68

• My PR includes a link to the issue that I am addressing

Documentation Change Checklist

• Any updated docstrings use the NumPy docstring format

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.68%. Comparing base (3dea29f) to head (e59c6f9).
Report is 72 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #85   +/-   ##
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  Coverage   98.68%   98.68%           
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  Files          15       15           
  Lines         836      836           
=======================================
  Hits          825      825           
  Misses         11       11           

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[github-actions]

Before [3dea29f]	After [5f446f9]	Ratio	Benchmark (Parameter)
60.7±3ms	67.9±2ms	~1.12	benchmarks.ReassignHalfOfNestedSeries.time_run
9.10±0.3ms	9.45±0.1ms	1.04	benchmarks.NestedFrameAddNested.time_run
6.53±0.1ms	6.75±0.2ms	1.03	benchmarks.NestedFrameQuery.time_run
272M	278M	1.02	benchmarks.ReassignHalfOfNestedSeries.peakmem_run
255M	258M	1.01	benchmarks.AssignSingleDfToNestedSeries.peakmem_run
33.6±4ms	33.8±2ms	1.01	benchmarks.AssignSingleDfToNestedSeries.time_run
89.6M	90.9M	1.01	benchmarks.NestedFrameQuery.peakmem_run
86.2M	86.4M	1.00	benchmarks.NestedFrameAddNested.peakmem_run
89.6M	89.6M	1.00	benchmarks.NestedFrameReduce.peakmem_run
5.36±0.2ms	5.36±0.05ms	1.00	benchmarks.NestedFrameReduce.time_run

Click here to view all benchmarks.

[dougbrn]

Looks great, just found two minor nits