Issue with Subtensor

Questions
1

Hi!

I am trying hard to adapt the fairly simple notebook Introduction of pymc3.ode API seen here.

I wrote the code below but it fails even before using the model.

import arviz as az
import matplotlib.pyplot as plt
import numpy as np
import pymc3 as pm
import theano
from io import BytesIO
from pymc3.ode import DifferentialEquation
from scipy.integrate import odeint
from scipy.optimize import curve_fit

plt.style.use('seaborn-darkgrid')

n_conditions = 2
n_genes = 12
n_replicats = 4
times = np.array([0., 0.5, 1., 3.5, 6.5, 9.25, 12.5, 18.5, 22.5, 26.5, 30.5])
n_timeintervals = times.size-1 # = 10
n_timesteps = times.size # = 11

Binary = open('data.txt').read().replace(',', '.').encode()
expr = np.genfromtxt(BytesIO(Binary), missing_values = 'NA', filling_values = np.nan, skip_header = 1)
exprtg = expr[: , 3 : ].reshape(7, n_timesteps, n_genes)
exprtgTF = expr[: , 7 ].reshape(7, n_timesteps)
mu0  = np.nanmean(exprtg[:, 0, :], axis = (0, 1))

def geneexpression(mu, t, parameters):
    alpha = np.zeros(n_genes)
    beta  = np.zeros(n_genes)
    gamma = np.zeros(n_genes)
    delta = np.zeros(n_genes)
    for i in range(n_genes):
        print(alpha[i], parameters[4*i])
        alpha[i] = parameters[4*i]
        beta[i]  = parameters[4*i+1]
        gamma[i] = parameters[4*i+2]
        delta[i] = parameters[4*i+3]

    eta = np.concatenate(([1.], parameters[4*n_genes : ]))

    current_index = np.searchsorted(times, t, side='right')-1
    if current_index >= n_timeintervals:
        current_index -= 1
    current_eta = eta[current_index]
    dmu_dt = alpha + beta * current_eta / (gamma + current_eta) - delta * mu
    return dmu_dt # return statement of geneexpression

ode_model = DifferentialEquation(
    func=geneexpression,
    times=times,
    n_states=n_genes,
    n_theta=4*n_genes + n_timeintervals-1, # eta is normalized with eta=1. on the first time interval
    t0=0
)

Data is pasted here.
It fails with the error

ValueError: setting an array element with a sequence.

on line

alpha[i] = parameters[4*i]

so my understanding is that I cannot access to a given parameter with the bracket notation. How should I do then?