class_docstr: Context manager for making an algorithm instance available to catalyst API
  functions within a scoped block.
docstr: Set the given algo instance, storing any previously-existing instance.
code: def __enter__(self):
      """
      Set the given algo instance, storing any previously-existing instance.
      """
      self.old_algo_instance = get_algo_instance()
      set_algo_instance(self.algo_instance)
  
file_path: catalyst/catalyst/utils/api_support.py
imports: from functools import wraps
  import catalyst.api
  from catalyst.utils.algo_instance import get_algo_instance, set_algo_instance
label_desc: Use image node_id 2 for calling the ZiplineAPI obj's underlying member method code with example usage: obj.__enter__() without return types