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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 main(items=None, printmd=None, printcal=False, found=False, save=None, download=None, requestor_pays=False, **kwargs):
 """ Main function for performing a search """

    
    if items is None:
        ## if there are no items then perform a search
        search = Search.search(**kwargs)
        if found:
            num = search.found()
            print('%s items found' % num)
            return num
        items = search.items()
    else:
        # otherwise, load a search from a file
        items = Items.load(items)

    print('%s items found' % len(items))

    # print metadata
    if printmd is not None:
        print(items.summary(printmd))

    # print calendar
    if printcal:
        print(items.calendar())

    # save all metadata in JSON file
    if save is not None:
        items.save(filename=save)

    # download files given `download` keys
    if download is not None:
        if 'ALL' in download:
            # get complete set of assets
            download = set([k for i in items for k in i.assets])
        for key in download:
            items.download(key=key, path=config.DATADIR, filename=config.FILENAME, requestor_pays=requestor_pays)

    return items