Note that the format can be autodetected

[interfect]

The format for from_file doesn't actually default to MP3. See here:

pydub/pydub/audio_segment.py

Lines 659 to 666 in 23779fd

	# If format is not defined
	# ffmpeg/avconv will detect it automatically
	if format:
	conversion_command += ["-f", format]
	if codec:
	# force audio decoder
	conversion_command += ["-acodec", codec]

This updates the documentation to reflect that.