def find_spans_pdb(pdb: MyPDB) -> list:
memb_vec = []
for res in pdb.iter_all_res():
memb_vec.append( res.memb_z is not None )
spans = []
chain, start, end, ori = pdb.get_res(1).chain, -1, -1, 'fwd'
tm_open = False
for i in range(len(memb_vec)):
if pdb.get_res(i+1).chain != chain and tm_open:
end = i
ori = 'fwd' if pdb.get_res(start).memb_z < 0 and pdb.get_res(end) > 0 else 'rev'
spans.append([start, end, ori])
tm_open = False
if memb_vec[i] and not tm_open:
start = i + 1
tm_open = True
if not memb_vec[i] and tm_open:
end = i-1
ori = 'fwd' if pdb.get_res(start).memb_z < 0 and pdb.get_res(end) > 0 else 'rev'
spans.append([start, end, ori])
tm_open = False
chain = pdb.get_res(i+1).chain
if tm_open:
spans.append([start, i+1, ori])
return spans
