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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 _get_all_packages(mirror=DEFAULT_MIRROR,
                      cyg_arch='x86_64'):
    '''
    Return the list of packages based on the mirror provided.
    '''
    if 'cyg.all_packages' not in __context__:
        __context__['cyg.all_packages'] = {}
    if mirror not in __context__['cyg.all_packages']:
        __context__['cyg.all_packages'][mirror] = []
    if not __context__['cyg.all_packages'][mirror]:
        pkg_source = '/'.join([mirror, cyg_arch, 'setup.bz2'])

        file_data = _urlopen(pkg_source).read()
        file_lines = bz2.decompress(file_data).decode('utf_8',
                                                      errors='replace'
                                                     ).splitlines()

        packages = [re.search('^@ ([^ ]+)', line).group(1) for
                    line in file_lines if re.match('^@ [^ ]+', line)]

        __context__['cyg.all_packages'][mirror] = packages

    return __context__['cyg.all_packages'][mirror]