public ExponentialBackoffBuilder initialDelayMillis(long initialDelayMillis) {
        checkArgument(initialDelayMillis >= 0, "initialDelayMillis: %s (expected: >= 0)", initialDelayMillis);
        this.initialDelayMillis = initialDelayMillis;
        return this;
    }
Sets the initial delay in milliseconds for the Exponential {@link Backoff}.

<p>The initial delay is the starting value for the exponential backoff, determining
the delay before the first retry. Subsequent delays will increase exponentially
based on the multiplier.</p>

@param initialDelayMillis the initial delay in milliseconds
core/src/main/java/com/linecorp/armeria/client/retry/ExponentialBackoffBuilder.java