code: def build_act(cls: Type[_Block], node: ast.stmt, test_func_node: ast.FunctionDef) -> _Block:
          
          add_node_parents(test_func_node)
          # Walk up the parent nodes of the parent node to find test's definition.
          act_block_node = node
          while act_block_node.parent != test_func_node:  # type: ignore
              act_block_node = act_block_node.parent  # type: ignore
          return cls([act_block_node], LineType.act)
docs: Act block is a single node - either the act node itself, or the node
          that wraps the act node.