docstr: Estimated signal without diffusion-weighting.
  
  Returns
  -------
  S0 : numpy.ndarray
docstr_tok: ["Estimated","signal","without","diffusion-weighting",".","Returns","--","--","--","-","S0",":","numpy.ndarray"]
code: def S0_hat(self):
      """Estimated signal without diffusion-weighting.
  
      Returns
      -------
      S0 : numpy.ndarray
      """
      S0 = np.exp(self.params[..., 0])
      return S0
  
imports: from warnings import warn
  import numpy
  from dipy.reconst.base import ReconstModel
  from dipy.reconst.dti import auto_attr
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 3 for calling the QtiFit obj's underlying member method code with example usage: obj.S0_hat() and returns: S0