You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: tests.rs
    path of file: ./repos/vector/src/sinks/splunk_hec/metrics
    
    the code of the file until where you have to start completion: use std::{collections::BTreeSet, sync::Arc};

use chrono::{DateTime, Utc};
use futures_util::StreamExt;
use serde_json::{json, Value as JsonValue};
use vector_lib::{
    event::{Event, Metric, MetricKind, MetricValue},
    metric_tags, ByteSizeOf,
};
use vrl::owned_value_path;

use super::sink::{process_metric, HecProcessedEvent};
use crate::sinks::splunk_hec
    
fn test_process_metric_unsupported_type_returns_none() {
    let mut values = BTreeSet::new();
    values.insert(String::from("value1"));

    let metric = Metric::new(
        "example-set",
        MetricKind::Absolute,
        MetricValue::Set { values },
    );

    let event_byte_size = metric.size_of();
    let sourcetype = None;
    let source = None;
    let index = None;
    let default_namespace = None;
    assert!(process_metric(
        metric,
        event_byte_size,
        sourcetype,
        source,
        index,
        Some(&owned_value_path!("host_key")),
        default_namespace
    )
    .is_none());
}