added doctests and comments
added doctests and comments

kaushik94/sympy,drufat/sympy,chaffra/sympy,aktech/sympy,aktech/sympy,chaffra/sympy,yashsharan/sympy,souravsingh/sympy,rahuldan/sympy,skidzo/sympy,jaimahajan1997/sympy,kaushik94/sympy,drufat/sympy,yashsharan/sympy,sampadsaha5/sympy,postvakje/sympy,skidzo/sympy,jaimahajan1997/sympy,madan96/sympy,souravsingh/sympy,rahuldan/sympy,postvakje/sympy,yashsharan/sympy,skidzo/sympy,madan96/sympy,souravsingh/sympy,aktech/sympy,postvakje/sympy,madan96/sympy,drufat/sympy,rahuldan/sympy,jaimahajan1997/sympy,sampadsaha5/sympy,sampadsaha5/sympy,chaffra/sympy,kaushik94/sympy