added tests for periodicity after helper
added tests for periodicity after helper

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