### How am I using definite_integral wrong?

I'm attempting to evaluate the definite integral of a symbolic function, and I'm getting a type error that I don't understand.

Here's my script:

```
from sage.symbolic.integration.integral import definite_integral
### random variables
xi = var('xi'); assume(xi >= 0)
tau, eta = var('tau', 'eta'); assume(tau > 0); assume(eta > 0)
p1 = var('p1'); assume(p1 >= 0); assume(p1 <=1)
### expressions
h(p1, alpha, beta) = p1^(1/3 - 1) * (1 - p1)^(1/3 - 1)
k(p1, xi) = (1 - exp(-p1 * xi)) * exp(-p1 * xi)
hk = h * k
### evaluate
print(hk)
print(type(hk))
definite_integral(hk, p1, 0, 1)
```

The call to `print(type(hk))`

returns `<class 'sage.symbolic.expression.Expression'>`

, which is what I expect. However, the call to `definite_integral(hk, p1, 0, 1)`

returns a lengthy error message featuring:

```
TypeError: cannot coerce arguments: no canonical coercion from Callable function ring with arguments (p1, alpha, beta, xi) to Symbolic Ring
```

I'm not sure what's going on with the types here, and I'd like to understand that so I can get this to work and also avoid making such mistakes in the future.

Thanks in advance,
A beginner