def mark_sentence_boundaries(sequences, drop=<NUM_LIT:0.0>):  
for sequence in sequences:<EOL><INDENT>sequence.insert(<NUM_LIT:0>, "<STR_LIT>")<EOL>sequence.insert(<NUM_LIT:0>, "<STR_LIT>")<EOL>sequence.append("<STR_LIT>")<EOL>sequence.append("<STR_LIT>")<EOL><DEDENT>return sequences, None<EOL>
Pad sentence sequences with EOL markers.