Amended missing docstring in frv.py
Amended missing docstring in frv.py

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