Parses arguments, returns (options, args).

def parse_args(args=None):
    """Parses arguments, returns (options, args)."""
    import sys
    from argparse import ArgumentParser
    from path_helpers import path

    if args is None:
        args = sys.argv

    parser = ArgumentParser(description='Example app for drawing shapes from '
                            'dataframe, scaled to fit to GTK canvas while '
                            'preserving aspect ratio (a.k.a., aspect fit).')
    parser.add_argument('svg_filepath', type=path, default=None)
    parser.add_argument('-p', '--padding-fraction', type=float, default=0)

    args = parser.parse_args()
    return args