Question: How to plot a clean graph of the argument of a complex number?

to make this image I have just defined

f := (x, y) -> piecewise(y <> 0, 2*arctan((sqrt(y^2 + x^2) - x)/y), 0 < x and y = 0, 0, x < 0 and y = 0, Pi, x = 0 and y = 0, undefinied)

contourplot(f(x, y), x = -1 .. 1, y = -Pi .. Pi, color = black, numpoints = 10000);

ofc I could define z:=x+I*y and take

contourplot(argument(z), x = -1 .. 1, y = -Pi .. Pi, color = black, numpoints = 10000);

but I don't know how to delete this "tail" , I want to show only the ray (I thought that definition of argument in MAPLE is problematic so I redefined it but it doesn't matter)

I need this to create phase portrait and make better visualisation for complex function in MAPLE, so I would like to make and argument of function as two variable function which is modified such that this "tail" disappeared, thanks in advance