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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 create_inputlist(arglist):
 """Read lines from a file and makes a list of file names. Removes whitespace and lines that start with '#' Recursively read all files with the extension '.lst' """

    lines = []
    if isinstance(arglist, list):
        for arg in arglist:
            if os.path.splitext(arg)[1] == '.lst':
                lines += readlines(arg)
            else:
                lines.append(arg)
    elif is_null(arglist):
        pass
    else:
        if os.path.splitext(arglist)[1] == '.lst':
            lines += readlines(arglist)
        else:
            lines.append(arglist)
    return lines