The leading underscore is meant to distinguish private (for internal
use only) APIs from public (for external use) APIs. One can argue about
where the line between public and private should be, but if something
is used from other modules (as with read_variable_length_integer) it's
not really private IMHO.
In scripts (like __main__) it also doesn't make much sense to use
leading underscores, because the entire file is never meant to be used
by external code.
Previously, the types of instance attributes were annotated with the
first assignment of each attribute. The standard way to annotate
instance attributes is to do so at class level without assigning any
value.
