import re
rx = r'\b([A-Z](?:\.[A-Z])+\b(?:\.(?![A-Z]))?)|\.'
s = ' A.B.C.D.E. FGH.IJ K.L.M.NO PQ.R.S T.U.VWXYZ'
print( re.sub(rx, lambda x: x.group(1).replace('.', '') if x.group(1) else ' ', s.strip()) )
aW1wb3J0IHJlCnJ4ID0gcidcYihbQS1aXSg/OlwuW0EtWl0pK1xiKD86XC4oPyFbQS1aXSkpPyl8XC4nCnMgPSAnIEEuQi5DLkQuRS4gRkdILklKIEsuTC5NLk5PIFBRLlIuUyBULlUuVldYWVonCnByaW50KCByZS5zdWIocngsIGxhbWJkYSB4OiB4Lmdyb3VwKDEpLnJlcGxhY2UoJy4nLCAnJykgaWYgeC5ncm91cCgxKSBlbHNlICcgJywgcy5zdHJpcCgpKSAp