docstr: Average of microscopic diffusion tensors' outer products with
  themselves.
  
  Returns
  -------
  mean_d_sq : numpy.ndarray
  
  Notes
  -----
  Average of microscopic diffusion tensors' outer products with themselves
  is calculated as
  
      .. math::
  
          \langle \mathbf{D} \otimes \mathbf{D} 
  angle = \mathbb{C} +
          \langle \mathbf{D} 
  angle \otimes \langle \mathbf{D} 
  angle
docstr_tok: ["Average","of","microscopic","diffusion","tensors","'","outer","products","with","themselves",".","Returns","--","--","--","-","mean_d_sq",":","numpy.ndarray","Notes","--","--","-","Average","of","microscopic","diffusion","tensors","'","outer","products","with","themselves","is","calculated","as","..","math",":",":","\\langle","\\mathbf","{","D","}","\\otimes","\\mathbf","{","D","}","angle","=","\\mathbb","{","C","}","+","\\langle","\\mathbf","{","D","}","angle","\\otimes","\\langle","\\mathbf","{","D","}","angle"]
code: def mean_d_sq(self):
      """Average of microscopic diffusion tensors' outer products with
      themselves.
  
      Returns
      -------
      mean_d_sq : numpy.ndarray
  
      Notes
      -----
      Average of microscopic diffusion tensors' outer products with themselves
      is calculated as
  
          .. math::
  
              \langle \mathbf{D} \otimes \mathbf{D} \rangle = \mathbb{C} +
              \langle \mathbf{D} \rangle \otimes \langle \mathbf{D} \rangle
      """
      mean_d_sq = (
          from_21x1_to_6x6(self.params[..., 7::, np.newaxis])
          + self.d_sq
      )
      return mean_d_sq
  
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 9 for calling the QtiFit obj's underlying member method code with example usage: obj.mean_d_sq() and returns: mean_d_sq