AWS supports the following Ruby runtimes:

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Name | Identifier | SDK for Ruby | Operating system
-- | -- | -- | --
Ruby 2.7 | ruby2.7 | 3.0.1 | Amazon Linux 2
Ruby 2.5 | ruby2.5 | 3.0.1 | Amazon Linux

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Currently, `localstack/lambda` only contains the `ruby2.5` tag. Will the 2.7 runtime be supported in the (near) future?
temp_mv_dict = defaultdict(list)
    for key in elements:
        if isinstance(key, (list, tuple)):
            key, value = key
        else:
            value = elements[key]
        key = to_str(key)
        temp_mv_dict[key].append(value)
    return dict((k, tuple(v)) for k, v in temp_mv_dict.items())
def get_handler_file_from_name(handler_name, runtime=LAMBDA_DEFAULT_RUNTIME):
    if runtime.startswith(LAMBDA_RUNTIME_PROVIDED):
        return 'bootstrap'
    delimiter = '.'
    if runtime.startswith(LAMBDA_RUNTIME_NODEJS):
        file_ext = '.js'
    elif runtime.startswith(LAMBDA_RUNTIME_GOLANG):
        file_ext = ''
    elif runtime.startswith(tuple(DOTNET_LAMBDA_RUNTIMES)):
        file_ext = '.dll'
        delimiter = ':'
    elif runtime.startswith(LAMBDA_RUNTIME_RUBY):
        file_ext = '.rb'
    else:
        handler_name = handler_name.rpartition(delimiter)[0].replace(delimiter, os.path.sep)
        file_ext = '.py'
    return '%s%s' % (handler_name.split(delimiter)[0], file_ext)