'Partial Derivative in sympy without Subs()

I would like to express an arbitrary function's complete derivative in terms of its partial derivatives. Required expression

Using Sympy:

x = symbols("x")
f, y = symbols("f, y", cls=Function)
f(t,y(t)).diff(t)

However this returns an expression with a substitution term in it. Retrieved expression.

How do I achieve the required expression with sympy?

python sympy

Sources

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