public final void setAutomaticSeparator(String automaticSeparator) {
        this.automaticSeparator = Objects.requireNonNull(automaticSeparator);
    }
Sets the automatic separator that is written to a {@code SymbolWriter}
each time the writer is reused.

<p>The default line separator is a newline ("\n"), but some
implementations may wish to use an alternative value (e.g., "\r\n") or
to disable the newline separator altogether by proving an empty string.

@param automaticSeparator The non-null line separator to use.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/WriterDelegator.java