Refactorization and optimization about the deepcopy of ExecNodes which is not necessary
Refactor _get_leaves_ids by making a method DAG._alias_to_id
optimization of a deepcopy into a normal copy
because deepcopy is no longer used, an ExecNode can now actually be passed in parameters that are not serializable. However in this case the caching still is not possible
Description
Refactorization and optimization about the deepcopy of ExecNodes which is not necessary
_get_leaves_idsby making a methodDAG._alias_to_idFixes # (issue) solves #57