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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 add_external_library(library):
 """ Add a build option for selecting the internal or system copy of a library. Parameters library : str The name of the library. If the library is `foo`, the build option will be called `--use-system-foo`. """


    for command in ['build', 'build_ext', 'install']:
        add_command_option(command, str('use-system-' + library),
                           'Use the system {0} library'.format(library),
                           is_bool=True)