<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_all_migrations():
 """ Returns sorted list of all migrations. Returns: list of (int, str) tuples: first elem of the tuple is migration number, second if module name. """

    from . import migrations

    package = migrations
    prefix = package.__name__ + '.'
    all_migrations = []
    for importer, modname, ispkg in pkgutil.iter_modules(package.__path__, prefix):
        version = int(modname.split('.')[-1].split('_')[0])
        all_migrations.append((version, modname))

    all_migrations = sorted(all_migrations, key=lambda x: x[0])
    return all_migrations