I found a few students would write a DonorCollection class, but have it be a wrapper around their previous structure, without "proper" encapsulation.

that is, the class would be a namespace for the all their previous functions that worked with the donors structure, but kept the structure itself separate.

A little more discussion / clarity on the design might help this.

and a warning against:

def __init__(self, donors):
    self.donors = donors

where donors is the original donors structure, and there is no copy made.