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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_var(var, value):
    '''
    Add a new var to the make.conf. If using layman, the source line
    for the layman make.conf needs to be at the very end of the
    config. This ensures that the new var will be above the source
    line.
    '''
    makeconf = _get_makeconf()
    layman = 'source /var/lib/layman/make.conf'
    fullvar = '{0}="{1}"'.format(var, value)
    if __salt__['file.contains'](makeconf, layman):
        # TODO perhaps make this a function in the file module?
        cmd = ['sed', '-i', r'/{0}/ i\{1}'.format(
                    layman.replace('/', '\\/'),
                    fullvar),
               makeconf]
        __salt__['cmd.run'](cmd)
    else:
        __salt__['file.append'](makeconf, fullvar)