code: def _sample_oat(problem, N, num_levels=4):
      
      group_membership = np.asmatrix(np.identity(problem['num_vars'],
                                                 dtype=int))
  
      num_params = group_membership.shape[0]
      sample = np.zeros((N * (num_params + 1), num_params))
      sample = np.array([generate_trajectory(group_membership,
                                             num_levels)
                         for n in range(N)])
      return sample.reshape((N * (num_params + 1), num_params))
docs: Generate trajectories without groups
  
      Arguments
      ---------
      problem : dict
          The problem definition
      N : int
          The number of samples to generate
      num_levels : int, default=4
          The number of grid levels