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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 copy_files(filelist, destdir):
 """Copy a list of files to destdir, preserving directory structure. File names should be relative to the current working directory. """

    for filename in filelist:
        destfile = os.path.join(destdir, filename)
        # filename should not be absolute, but let's double-check
        assert destfile.startswith(destdir + os.path.sep)
        destfiledir = os.path.dirname(destfile)
        if not os.path.isdir(destfiledir):
            os.makedirs(destfiledir)
        if os.path.isdir(filename):
            os.mkdir(destfile)
        else:
            shutil.copy2(filename, destfile)