MAINT: Refactor Python engine empty line funcs (#15946)
MAINT: Refactor Python engine empty line funcs (#15946)

The Python engine's _empty and _check_empty
methods were uninformative and undocumented.

This commit renames them to _is_line_empty
and _remove_empty_lines respectively and
provides appropriate documentation.
jreback/pandas,pratapvardhan/pandas,GuessWhoSamFoo/pandas,jreback/pandas,harisbal/pandas,TomAugspurger/pandas,gfyoung/pandas,rs2/pandas,pandas-dev/pandas,dsm054/pandas,jorisvandenbossche/pandas,linebp/pandas,MJuddBooth/pandas,pandas-dev/pandas,gfyoung/pandas,kdebrab/pandas,cbertinato/pandas,cython-testbed/pandas,kdebrab/pandas,jorisvandenbossche/pandas,linebp/pandas,winklerand/pandas,harisbal/pandas,gfyoung/pandas,cbertinato/pandas,Winand/pandas,louispotok/pandas,jmmease/pandas,pratapvardhan/pandas,linebp/pandas,cython-testbed/pandas,jorisvandenbossche/pandas,MJuddBooth/pandas,Winand/pandas,jmmease/pandas,zfrenchee/pandas,DGrady/pandas,louispotok/pandas,DGrady/pandas,winklerand/pandas,dsm054/pandas,winklerand/pandas,linebp/pandas,pratapvardhan/pandas,louispotok/pandas,toobaz/pandas,harisbal/pandas,gfyoung/pandas,dsm054/pandas,nmartensen/pandas,winklerand/pandas,TomAugspurger/pandas,Winand/pandas,MJuddBooth/pandas,gfyoung/pandas,MJuddBooth/pandas,winklerand/pandas,datapythonista/pandas,linebp/pandas,MJuddBooth/pandas,pratapvardhan/pandas,datapythonista/pandas,nmartensen/pandas,zfrenchee/pandas,pratapvardhan/pandas,jreback/pandas,pandas-dev/pandas,amolkahat/pandas,zfrenchee/pandas,cbertinato/pandas,jmmease/pandas,nmartensen/pandas,GuessWhoSamFoo/pandas,zfrenchee/pandas,jmmease/pandas,TomAugspurger/pandas,jmmease/pandas,winklerand/pandas,jorisvandenbossche/pandas,toobaz/pandas,cython-testbed/pandas,harisbal/pandas,kdebrab/pandas,dsm054/pandas,harisbal/pandas,cython-testbed/pandas,zfrenchee/pandas,rs2/pandas,toobaz/pandas,amolkahat/pandas,cbertinato/pandas,dsm054/pandas,pandas-dev/pandas,amolkahat/pandas,GuessWhoSamFoo/pandas,DGrady/pandas,amolkahat/pandas,jreback/pandas,jreback/pandas,DGrady/pandas,rs2/pandas,louispotok/pandas,nmartensen/pandas,nmartensen/pandas,kdebrab/pandas,toobaz/pandas,datapythonista/pandas,GuessWhoSamFoo/pandas,datapythonista/pandas,cbertinato/pandas,Winand/pandas,DGrady/pandas,toobaz/pandas,GuessWhoSamFoo/pandas,amolkahat/pandas,Winand/pandas,rs2/pandas,nmartensen/pandas,TomAugspurger/pandas,louispotok/pandas,cython-testbed/pandas,linebp/pandas,DGrady/pandas,Winand/pandas,kdebrab/pandas,jmmease/pandas