Replace incomplete example in intro_to_sparql.rst

[tombaker]

Fixes incomplete example in intro_to_sparql.rst

TimBL's FOAF page no longer has any foaf:knows triples, so a beginner will not be able to reproduce the results obtained in the example, as is. The query string is also missing a PREFIX binding for foaf:.

Proposed Changes

• As TimBL's FOAF page no longer has any foaf:knows triples, uses Danbri's FOAF page, which does.
• Minor rewordings in third paragraph, for clarity.
• Assigns query string to variable so that it can be used in a second example (below).
• Minor rewording in paragraph starting "The results are tuples...".
• Provides second, short example, illustrating the use of initNs
• Uses f-string illustrating different ways to access result values.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[coveralls]

Coverage remained the same at 75.705% when pulling a4a9d06 on tombaker:master into 58b23fd on RDFLib:master.

[nicholascar]

Hi @tombaker thnks very much for the updated docco! I am preparing a rather large total doc update in readiness for a 6.0.0 release of RDFlib soon, but I hand't picked up on this particular issue so this is very much appreciated.

[tombaker]

@nicholascar Thank you for letting me know that my modest contributions are appreciated :-) If I come across other places where small improvements might be made, will submit them for consideration.