save state
formatting
try to tackle remaining obligations
work on unproven obligation
try to close missing proofs
add proof got peroperty GHI_equal.
remove old ABC_equal proof attempts
remove admit in property DEF_equal to indicate proof gap
add assertion on stream->size
first versionof DEF_equal proof (with two admits)
add assertion about separation
resolve two admits
remove old proof attempt
remove final admit in DEF_equal