class_docstr: Test statistic holder for Wald-type tests
  
  Parameters
  ----------
  stat : float
      The test statistic
  df : int
      Degree of freedom.
  null : str
      A statement of the test's null hypothesis
  alternative : str
      A statement of the test's alternative hypothesis
  name : str, default "" (empty)
      Name of test
code: def __init__(
      self,
      stat: float,
      df: int,
      null: str,
      alternative: str,
      name: str = "",
  ) -> None:
      self._stat = stat
      self._null = null
      self._alternative = alternative
      self.df: int = df
      self._name = name
      self.dist = chi2(df)
      self.dist_name: str = f"chi2({df})"
  
file_path: arch/arch/utility/testing.py
imports: from __future__ import annotations
  from functools import cached_property
  from scipy.stats import chi2
label_desc: Use image node_id 1 to create a new WaldTestStatistic object  with example: obj = WaldTestStatistic(stat, df, null, alternative, name)