Why am I getting a different solution on SageMath for an ODE compared to when I work it by hand?

edit

I am solving the separable linear ODE y'(x)+y(x)'-1 = 0 and SageMath returns the solution:

(_C + e^x)*e^(-x)

However, when I work it by hand I get this answer with a minor difference:

y = -e^(-x)C +1

Where is the negative sign in the SageMath solution?

Here is my code:

y = function('y')(x) 
x = var('x')  
de = diff(y,x)+y-1 == 0 
desolve(de,y)