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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_standard_vars(cls, context, variant, build_type, install, build_path, install_path=None):
 """Returns a standard set of environment variables that can be set for the build system to use """

        from rez.config import config

        package = variant.parent
        variant_requires = map(str, variant.variant_requires)

        if variant.index is None:
            variant_subpath = ''
        else:
            variant_subpath = variant._non_shortlinked_subpath

        vars_ = {
            'REZ_BUILD_ENV': 1,
            'REZ_BUILD_PATH': build_path,
            'REZ_BUILD_THREAD_COUNT': package.config.build_thread_count,
            'REZ_BUILD_VARIANT_INDEX': variant.index or 0,
            'REZ_BUILD_VARIANT_REQUIRES': ' '.join(variant_requires),
            'REZ_BUILD_VARIANT_SUBPATH': variant_subpath,
            'REZ_BUILD_PROJECT_VERSION': str(package.version),
            'REZ_BUILD_PROJECT_NAME': package.name,
            'REZ_BUILD_PROJECT_DESCRIPTION': (package.description or '').strip(),
            'REZ_BUILD_PROJECT_FILE': package.filepath,
            'REZ_BUILD_SOURCE_PATH': os.path.dirname(package.filepath),
            'REZ_BUILD_REQUIRES': ' '.join(
                str(x) for x in context.requested_packages(True)
            ),
            'REZ_BUILD_REQUIRES_UNVERSIONED': ' '.join(
                x.name for x in context.requested_packages(True)
            ),
            'REZ_BUILD_TYPE': build_type.name,
            'REZ_BUILD_INSTALL': 1 if install else 0,
        }

        if install_path:
            vars_['REZ_BUILD_INSTALL_PATH'] = install_path

        if config.rez_1_environment_variables and \
                not config.disable_rez_1_compatibility and \
                build_type == BuildType.central:
            vars_['REZ_IN_REZ_RELEASE'] = 1

        return vars_