to fix issues and warnings

[kevin7lou]

to fix issues and warnings:

12:27:08 PM: /opt/build/repo/doc/Python-for-Data-Analysis/S2D00-data-structure.md:3: WARNING: duplicate label structure:index, other instance in /opt/build/repo/doc/Python-for-Data-Analysis/S1D00-getting-started.md
12:27:08 PM: ERROR: Execution Failed with traceback saved in /opt/build/repo/_build/html/reports/S2D05-lists.log
12:27:08 PM: ERROR: Execution Failed with traceback saved in /opt/build/repo/_build/html/reports/S2D06-tuples-and-strings.log
12:27:08 PM: ERROR: Execution Failed with traceback saved in /opt/build/repo/_build/html/reports/S2D09-pandas-dataframes.log
12:27:08 PM: /opt/build/repo/doc/Python-for-Data-Analysis/S3/S3D00-programming-constructs.md:3: WARNING: duplicate label structure:index, other instance in /opt/build/repo/doc/Python-for-Data-Analysis/S2D00-data-structure.md
12:27:08 PM: /opt/build/repo/tmp/intro.md:: WARNING: tableofcontents directive in document with no descendants [etoc.tableofcontents]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20002: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20008: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20018: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20024: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20034: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20040: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:08 PM: /opt/build/repo/tmp/python-for-data-analysis-index.ipynb:20046: WARNING: Non-consecutive header level increase; 0 to 3 [myst.header]
12:27:09 PM: looking for now-outdated files... none found
12:27:09 PM: pickling environment... done
12:27:09 PM: checking consistency... /opt/build/repo/tmp/intro.md: WARNING: document isn't included in any toctree
/opt/build/repo/tmp/python-for-data-analysis-index.ipynb: WARNING: document isn't included in any toctree