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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 minify_css_files():
 """ This command minified js files with UglifyCSS """

    for k, v in CSS_FILE_MAPPING.items():
        input_files = " ".join(v["input_files"])
        output_file = v["output_file"]

        uglifyjs_command = "uglifycss {input_files} > {output_file}".format(
            input_files=input_files,
            output_file=output_file
        )
        local(uglifyjs_command)