Refactor method to be a staticmethod, public
Add a len method on file
Change method signature on __upload_form_encoded; use ShardFile instead of open() call; make upload ShardFile compatible
Docstring fix
Optimize imports
Add two helper funcs, calculate_shards (to determine shard start and end positions, and parse_shard_size to determine a shard size in bytes from a predetermined string pattern
Use helper methods in upload CLI scenario
Add shard-size arg to CLI