code: def add_enum(self, name, choices):
          
          if not isinstance(choices, Iterable):
              raise ValueError('variable %s: choices must be iterable' % name)
          self.variables[name] = EnumVariable(name, choices)
docs: An enumeration-valued dimension.
  
          The base measure associated with this dimension is a categorical
          distribution with equal weight on each element in `choices`.