class_docstr: Relates the variance of a random variable to its mean. Defaults to 1.
  
  Methods
  -------
  call
      Returns an array of ones that is the same shape as `mu`
  
  Notes
  -----
  After a variance function is initialized, its call method can be used.
  
  Alias for VarianceFunction:
  constant = VarianceFunction()
  
  See Also
  --------
  statsmodels.genmod.families.family
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docstr: Default variance function
  
  Parameters
  ----------
  mu : array_like
      mean parameters
  
  Returns
  -------
  v : ndarray
      ones(mu.shape)
docstr_tok: ["Default","variance","function","Parameters","--","--","--","--","--","mu",":","array_like","mean","parameters","Returns","--","--","--","-","v",":","ndarray","ones","(","mu.shape",")"]
code: def __call__(self, mu):
      """
      Default variance function
  
      Parameters
      ----------
      mu : array_like
          mean parameters
  
      Returns
      -------
      v : ndarray
          ones(mu.shape)
      """
      mu = np.asarray(mu)
      return np.ones(mu.shape, np.float64)
  
file_path: statsmodels/statsmodels/genmod/families/varfuncs.py
imports: import numpy
label_desc: Use image node_id 1 for calling the VarianceFunction obj's underlying member method code with example usage: obj.__call__(mu) and returns: np