class_docstr: Class for results of tests of linear restrictions on coefficients in a model.
  
  This class functions mainly as a container for `t_test`, `f_test` and
  `wald_test` for the parameters of a model.
  
  The attributes depend on the statistical test and are either based on the
  normal, the t, the F or the chisquare distribution.
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docstr: Returns the confidence interval of the value, `effect` of the constraint.
  
  This is currently only available for t and z tests.
  
  Parameters
  ----------
  alpha : float, optional
      The significance level for the confidence interval.
      ie., The default `alpha` = .05 returns a 95% confidence interval.
  
  Returns
  -------
  ci : ndarray, (k_constraints, 2)
      The array has the lower and the upper limit of the confidence
      interval in the columns.
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code: def conf_int(self, alpha=0.05):
      """
      Returns the confidence interval of the value, `effect` of the constraint.
  
      This is currently only available for t and z tests.
  
      Parameters
      ----------
      alpha : float, optional
          The significance level for the confidence interval.
          ie., The default `alpha` = .05 returns a 95% confidence interval.
  
      Returns
      -------
      ci : ndarray, (k_constraints, 2)
          The array has the lower and the upper limit of the confidence
          interval in the columns.
      """
      if self.effect is not None:
          # confidence intervals
          q = self.dist.ppf(1 - alpha / 2.0, *self.dist_args)
          lower = self.effect - q * self.sd
          upper = self.effect + q * self.sd
          return np.column_stack((lower, upper))
      else:
          raise NotImplementedError("Confidence Interval not available")
  
imports: import numpy
  from scipy.stats import f
  from scipy.stats import t
  from scipy import stats
  from statsmodels.tools.tools import clean0, fullrank
  from statsmodels.stats.multitest import multipletests
label_desc: Use image node_id 2 for calling the ContrastResults obj's underlying member method code with example usage: obj.conf_int(alpha) and returns: np