Can heat capacity at constant volume for a gas decrease as temperature increases? [closed]

I found a function for the $$C_V$$ of a gas which is being heated under constant volume,but the function shows that the $$C_V$$ is decreasing. I was wondering if this is possible for any gas since I know the $$C_V$$ is supposed to increase with temperature. Is there any reason why this would happen?

• Handbook of Chemistry and Physics, Chemical Engineers' Handbook, NIST, Fundamentals of Engineering Thermodynamics (Moran et al) – Chet Miller Mar 29 '18 at 15:41

As temperature increases, it activates the rotational and vibrational degrees of freedom, so $\ce{Cv}$ increases with increase in temperature. The graph $\ce{CO2}$ would be: