# Check if function is symmetric

I found the is_Symmetric() function in a tutorial, but I tried to use this with s([2,1]), which is clearly symmetric, but this is what I got

```
from sage.combinat.sf.sfa import is_SymmetricFunction
R.<x1,x2,x3>=PolynomialRing(QQ,3); R
s = SymmetricFunctions(QQ).schur()
f=s([2,1]).expand(3,'x1,x2,x3')
print(f)
is_SymmetricFunction(f)
x1^2*x2 + x1*x2^2 + x1^2*x3 + 2*x1*x2*x3 + x2^2*x3 + x1*x3^2 + x2*x3^2
False
```

Can someone please help?