code: def __getitem__(self, index):
      model_params = self.model_params
      N = model_params.ndim
      if type(index) is not tuple:
          index = (index,)
      elif len(index) >= model_params.ndim:
          raise IndexError("IndexError: invalid index")
      index = index + (slice(None),) * (N - len(index))
      return type(self)(self.model, model_params[index])
  
imports: import warnings
  import numpy
  from scipy.optimize import least_squares, differential_evolution
  from dipy.reconst.base import ReconstModel
  from dipy.reconst.multi_voxel import multi_voxel_fit
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 2 for calling the IvimFit obj's underlying member method code with example usage: obj.__getitem__(index) and returns: type