FrEIA.modules.Split incorrect completion of missing dimension when initialized with section_sizes Sequence

[RussellALA]

When initializing the FrEIA.modules.Split module as follows:

dim_in = (10,)
split_dims = (4, 3)
m = Split(dim_in, split_dims)

We get m.split_size_or_sections == None
Expected behaviour: m.split_size_or_sections == (4, 3, 3)
Suggested fix:
Change l.70 of modules/graph_topology.py from section_sizes = list(section_sizes).append(l_dim - sum(section_sizes)) to section_sizes = list(section_sizes) + [l_dim - sum(section_sizes)]