code: def GetAll(cls, attr, value, e=0.000001, sort_by="__name__"):
          
          matched = list()
          for _, klass in cls.Subclasses(sort_by=sort_by):
              try:
                  if klass.__dict__[attr] == approx(value, e):
                      matched.append(klass)
              except:  # pragma: no cover
                  pass
  
          return matched
docs: Get all nested Constant class that met ``klass.attr == value``.
  
          :param attr: attribute name.
          :param value: value.
          :param e: used for float value comparison.
          :param sort_by: nested class is ordered by <sort_by> attribute.
  
          .. versionadded:: 0.0.5