docs: def blend(self, blend_recipe, join_base, join_blend):
          """Blend a recipe into the base recipe.
          This performs an inner join of the blend_recipe to the
          base recipe's SQL.
          """
          assert isinstance(blend_recipe, Recipe)
  
          self.blend_recipes.append(blend_recipe)
          self.blend_types.append('inner')
          self.blend_criteria.append((join_base, join_blend))
          self.dirty = True
          return self.recipe