code: def extend (name, values):
      
      assert isinstance(name, basestring)
      assert is_iterable_typed(values, basestring)
      name = add_grist (name)
      __validate_feature (name)
      feature = __all_features [name]
  
      if feature.implicit:
          for v in values:
              if v in __implicit_features:
                  raise BaseException ("'%s' is already associated with the feature '%s'" % (v, __implicit_features [v]))
  
              __implicit_features[v] = feature
  
      if values and not feature.values and not(feature.free or feature.optional):
          # This is the first value specified for this feature,
          # take it as default value
          feature.set_default(values[0])
  
      feature.add_values(values)
docs: Adds the given values to the given feature.