Added docstring to _test method in frv.py
Added docstring to _test method in frv.py

chaffra/sympy,jaimahajan1997/sympy,madan96/sympy,kaushik94/sympy,kaushik94/sympy,skidzo/sympy,yashsharan/sympy,kaushik94/sympy,jaimahajan1997/sympy,yashsharan/sympy,chaffra/sympy,yashsharan/sympy,skidzo/sympy,madan96/sympy,skidzo/sympy,madan96/sympy,chaffra/sympy,jaimahajan1997/sympy