Running pyflakes on `garmin_fit_sdk`, I found a possible issue in `decoder.py`:
decoder.py:96:16: use ==/!= to compare constant literals (str, bytes, int, float, tuple)
decoder.py:317:12: use ==/!= to compare constant literals (str, bytes, int, float, tuple)
decoder.py:697:12: use ==/!= to compare constant literals (str, bytes, int, float, tuple)
An example is
`file_header.header_size is 14`
The code works, but using `is` is incorrect.