title: Python ValueError: setting an array element with a sequence.I'm getting this value error and I don't know how to solve the issue
body: <pre><code>def simulate(self, timesteps, **kwargs):
      pos = {comp: i for i, comp in enumerate(kwargs)}
      population = np.zeros(len(pos), dtype='int')
  
      for comp in pos:
          population[pos[comp]] = kwargs[comp]  # line where the error is 
  
      values = []
      values.append(population)
  
      comps = list(self.transitions.nodes)
      time = np.arange(1, timesteps, 1, dtype='int')
  
      for t in time:
          pop = values[-1]
          new_pop = values[-1].copy()
          N = np.sum(pop)
  </code></pre>
  
  <p>I am having this value error and I'm not sure on how to fix it. Any suggestion </p>
  
  <p>Error happens when I call this, </p>
  
  <p>if population is None:
          population = SIR1.values_.iloc[-1].copy()
      else:
          population = pd.concat([population, SIR1.values_.iloc[-1]])</p>
  
  <pre><code>S0 = population.S
  I00 = population.I
  R0 = population.R
  
  Quarantine.simulate(365 - 74, S=S0, I=I00, R=R0) ### Line causing the error
  </code></pre>