code: def _append_zeros(self, initial_conditions, number_of_equations):
          
  
          if len(initial_conditions) < number_of_equations:
              initial_conditions = np.concatenate((initial_conditions,
                                                   [0.0] * (self.problem.number_of_equations - len(initial_conditions))))
          return initial_conditions
docs: If not all intial conditions specified, append zeros to them
             TODO: is this really the best way to do this?