I am trying to implement a synapse whose time-constant is computed by a function based on some input A. How can I do this?

```
import nengo
model = nengo.Network()
with model:
A = nengo.Ensemble(n_neurons=50, dimensions=1)
B = nengo.Ensemble(n_neurons=50, dimensions=1)
C = nengo.Ensemble(n_neurons=50, dimensions=1)
tau = nengo.Ensemble(n_neurons=50, dimensions=1)
def compute_tau(A):
tau = 35/(1+(0.04*A)**2)
return tau
nengo.Connection(A, tau, function=compute_tau)
```

But now I want to use this computed tau as the time constant in another synapse :

nengo.Connection(B, C, synapse=tau)

I noticed that synapse can’t take either a function or an ensemble as an argument. So how can I feed a changing time constant?