`FCM: NON-DROP FRAME` are missing from round-trip

[lofidevops]

Steps to reproduce:

• Read and then write an EDL file as follows:

with open("020_Test.edl") as read_file:
    test_edl = parser.parse(read_file)

    with open("outfile.edl", "w") as write_file:
        write_file.write(test_edl.to_string())

What should happen:

• Output file is near-identical to input

What happens instead:

• Most lines are near-identical (correct)
• FCM: NON-DROP FRAME lines are missing

020_Test.edl.txt outfile.edl.txt

[lofidevops]

This appears to be addressed by https://github.com/AdricEpic/python-edl/tree/cmx_conform