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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def validate_source(ident, comment=None):
    '''Validate a source for automatic harvesting'''
    source = get_source(ident)
    source.validation.on = datetime.now()
    source.validation.comment = comment
    source.validation.state = VALIDATION_ACCEPTED
    if current_user.is_authenticated:
        source.validation.by = current_user._get_current_object()
    source.save()
    schedule(ident, cron=current_app.config['HARVEST_DEFAULT_SCHEDULE'])
    launch(ident)
    return source