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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 get_default_arch(env):
 """Return the default arch to use for MSVS if no version was requested by the user through the MSVS_ARCH environment variable, select x86 Return ------ arch: str """

    arch = env.get('MSVS_ARCH', 'x86')

    msvs = InstalledVSMap.get(env['MSVS_VERSION'])

    if not msvs:
        arch = 'x86'
    elif not arch in msvs.get_supported_arch():
        fmt = "Visual Studio version %s does not support architecture %s"
        raise SCons.Errors.UserError(fmt % (env['MSVS_VERSION'], arch))

    return arch