headers = headersOf("www-authenticate", "Basic realm=\"protected area\""),
        body = "Please authenticate.",
      ),
    )
    server.enqueue(
      MockResponse(body = "Successful auth!"),
    )
    val credential = basic("username", "password")
    client =
      client.newBuilder()
        .authenticator(RecordingOkAuthenticator(credential, "Basic"))
        .build()

```

</div>

////

This information will be useful when learning about [Virtual Environments](virtual-environments.md){.internal-link target=_blank}.

## Conclusion

With this you should have a basic understanding of what **environment variables** are and how to use them in Python.

// StorageErr represents error generated by xlStorage call.
type StorageErr string

func (h StorageErr) Error() string {
	return string(h)
}

// Collection of basic errors.
var baseErrs = []error{
	errDiskNotFound,
	errFaultyDisk,
	errFaultyRemoteDisk,
}

var baseIgnoredErrs = baseErrs

// Is a one place function which converts all os.PathError

    contentSchema: Optional["SchemaOrBool"] = None
    # Ref: JSON Schema Validation 2020-12: https://json-schema.org/draft/2020-12/json-schema-validation.html#name-a-vocabulary-for-basic-meta
    # A Vocabulary for Basic Meta-Data Annotations
    title: Optional[str] = None
    description: Optional[str] = None
    default: Optional[Any] = None
    deprecated: Optional[bool] = None
    readOnly: Optional[bool] = None

Use `Response.challenges()` to get the schemes and realms of any authentication challenges. When fulfilling a `Basic` challenge, use `Credentials.basic(username, password)` to encode the request header.

=== ":material-language-kotlin: Kotlin"
    ```kotlin
      private val client = OkHttpClient.Builder()

import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Basic implementation of {@code Multiset<E>} backed by an instance of {@code
 * ObjectCountHashMap<E>}.
 *
 * <p>For serialization to work, the subclass must specify explicit {@code readObject} and {@code
 * writeObject} methods.
 *

		},
		config.HelpKV{
			Key:         target.ElasticUsername,
			Description: "username for Elasticsearch basic-auth",
			Optional:    true,
			Type:        "string",
			Sensitive:   true,
		},
		config.HelpKV{
			Key:         target.ElasticPassword,
			Description: "password for Elasticsearch basic-auth",
			Optional:    true,
			Type:        "string",
			Sensitive:   true,
			Secret:      true,
		},

        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature
            X509v3 Extended Key Usage: 
                TLS Web Client Authentication
            X509v3 Basic Constraints: critical
                CA:FALSE
    Signature Algorithm: ED25519
         7e:aa:be:ed:47:4d:b9:2f:fc:ed:7f:5a:fc:6b:c0:05:5b:f5:
         a0:31:fe:86:e3:8e:3f:49:af:6d:d5:ac:c7:c4:57:47:ce:97:

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.primitives.Doubles;

/**
 * A mutable object which accumulates paired double values (e.g. points on a plane) and tracks some
 * basic statistics over all the values added so far. This class is not thread safe.
 *
 * @author Pete Gillin
 * @since 20.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package etag

import (
	"context"
	"crypto/md5"
	"fmt"
	"hash"
	"io"
)

// Tagger is the interface that wraps the basic ETag method.
type Tagger interface {
	ETag() ETag
}

type wrapReader struct {
	io.Reader
	Tagger
}

var _ Tagger = wrapReader{} // compiler check

// ETag returns the ETag of the underlying Tagger.