printEvent("callStart");
  }

  @Override public void callEnd(Call call) {
    printEvent("callEnd");
  }

  ...
}
```

We can use this listener to race a pair of concurrent HTTP requests:

```java
Request washingtonPostRequest = new Request.Builder()
    .url("https://www.washingtonpost.com/")
    .build();
client.newCall(washingtonPostRequest).enqueue(new Callback() {

  /**
   * Returns a new equivalence relation for {@code F} which evaluates equivalence by first applying
   * {@code function} to the argument, then evaluating using {@code this}. That is, for any pair of
   * non-null objects {@code x} and {@code y}, {@code equivalence.onResultOf(function).equivalent(a,
   * b)} is true if and only if {@code equivalence.equivalent(function.apply(a), function.apply(b))}
   * is true.
   *

 *
 * All start/connect/acquire events will eventually receive a matching end/release event, either
 * successful (non-null parameters), or failed (non-null throwable). The first common parameters of
 * each event pair are used to link the event in case of concurrent or repeated events e.g.
 * `dnsStart(call, domainName)` → `dnsEnd(call, domainName, inetAddressList)`.
 *
 * Events are typically nested with this structure:
 *

     * Gets the query builder for this context.
     * @return The query builder.
     */
    public QueryBuilder getQueryBuilder() {
        return queryBuilder;
    }

    /**
     * Adds a field and text pair to the field log for tracking query terms.
     * @param field The field name.
     * @param text The query text for this field.
     */
    public void addFieldLog(final String field, final String text) {

import okio.Buffer
import okio.ForwardingSink
import okio.ForwardingSource
import okio.Sink
import okio.Socket
import okio.Source
import okio.buffer

/**
 * Transmits a single HTTP request and a response pair. This layers connection management and events
 * on [ExchangeCodec], which handles the actual I/O.
 */
class Exchange(
  internal val call: RealCall,
  internal val eventListener: EventListener,

old_dict = {
    "old key": "old value",
    "second old key": "second old value",
}
new_dict = {**old_dict, "new key": "new value"}
```

Here, `new_dict` will contain all the key-value pairs from `old_dict` plus the new key-value pair:

```Python
{
    "old key": "old value",
    "second old key": "second old value",
    "new key": "new value",
}
```

        if (StringUtil.isBlank(ruleString)) {
            return childUrlRuleMap.entrySet().stream().map(e -> new Pair<>(e.getKey(), e.getValue()));
        }
        return Arrays.stream(ruleString.split(","))
                .map(s -> s.split(":"))
                .filter(v -> v.length == 2)
                .map(v -> new Pair<String, String>(v[0].trim(), v[1].trim()));
    }

    /**

private val TOKEN_DELIMITERS = "\t ,=".encodeUtf8()

/**
 * Parse RFC 7235 challenges. This is awkward because we need to look ahead to know how to
 * interpret a token.
 *
 * For example, the first line has a parameter name/value pair and the second line has a single
 * token68:
 *
 * ```
 * WWW-Authenticate: Digest foo=bar
 * WWW-Authenticate: Digest foo=
 * ```
 *

     *
     * @param css the CSS class name to match
     */
    public void setCss(final String css) {
        this.css = css;
    }

    /**
     * Sets a custom attribute name-value pair that this pruned tag should match.
     *
     * @param name the attribute name to match
     * @param value the attribute value to match
     */
    public void setAttr(final String name, final String value) {

import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.codelibs.core.io.FileUtil;
import org.codelibs.core.lang.StringUtil;
import org.codelibs.core.misc.Pair;
import org.codelibs.core.misc.Tuple3;
import org.codelibs.fess.exception.FessSystemException;
import org.codelibs.fess.mylasta.direction.FessConfig;
import org.codelibs.fess.unit.UnitFessTestCase;