使用plot_implicit（sympy）时错误的绘图显示

I'm given a spherical tank (radius R = 1m), completely filled with water. When I open the tank at the bottom, water flows out with a rate I = 1 litre per second. What I want is plotting the fill height h as a function of time t. I end up with an implicit equation, which can't be analytically solved for h (at least I'm told, but got no time for maths atm):I'm given a spherical tank (radius R = 1m), com