### Defining a function of the form $f(x_1,x_2,...,x_n)=\sum_{i=0}^n x_i$

How can I define a function of the form
$$f(x_1,x_2,...,x_n)=\sum_{i=0}^n x_i$$
I tried the following

`sage: n = 2`

`sage: x = [ var('x_%d' % i) for i in range(n) ]`

`sage: f(x)=sum(x[i],i,0,n)`

The last line gives me the error

"TypeError: 'sage.symbolic.expression.Expression' object does not support indexing".