Translate a list of entities to a list of their (unique) parents.

Unfold entities list to a child level (e.g. residues in chain).

Unfold a list of entities to a list of entities of another level. E.g.:

list of atoms -> list of residues list of modules -> list of atoms list of residues -> list of chains

• entity_list - list of entities or a single entity
• target_level - char (A, R, C, M, S)

Note that if entity_list is an empty list, you get an empty list back:

 >>> unfold_entities([], "A")
 []

Return a list of the unique items in the given iterable.

Order is NOT preserved.