```console
// Create an env var MY_NAME in line for this program call
$ MY_NAME="Wade Wilson" python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python

// The env var no longer exists afterwards
$ python main.py

Hello World from Python
```

</div>

/// tip

//
// Some types of a queries are not valid. For example, an aggregation
// function combined with a row function is meaningless ("AVG(s.Age) +
// s.Salary"). Analysis determines if such a scenario exists so an
// error can be returned.

var (
	// Fatal error for query processing.
	errNestedAggregation      = errors.New("Cannot nest aggregations")
	errFunctionNotImplemented = errors.New("Function is not yet implemented")

    return mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    // TODO: move this to invariant checks once the appropriate hook exists?
    super.expectContents(expected);
    for (Entry<K, V> entry : expected) {
      assertEquals(
          "Wrong value for key " + entry.getKey(), entry.getValue(), getMap().get(entry.getKey()));
    }
  }

These types that have internal types are called "**generic**" types. And it's possible to declare them, even with their internal types.

To declare those types and the internal types, you can use the standard Python module `typing`. It exists specifically to support these type hints.

#### Newer versions of Python { #newer-versions-of-python }

   *
   * <p>Under Android VMs, the methods for retrieving type-use annotations don't exist. This means
   * that {@link NullPointerTester} may misbehave under Android when used on classes that rely on
   * type-use annotations.
   *
   * <p>Under j2objc, the necessary APIs exist, but some (perhaps all) return stub values, like

     * @return number of keys in memory
     */
    public int getKeyCount() {
        return sessionKeys.size();
    }

    /**
     * Check if a session key exists
     *
     * @param sessionId session identifier
     * @return true if key exists
     */
    public boolean hasSessionKey(String sessionId) {
        checkNotClosed();

                logger.info("Created storage bucket: {}", bucket);
            }
        } catch (final Exception e) {
            logger.warn("Failed to ensure bucket exists: {}", bucket, e);
        }
    }

    @Override
    public boolean isAvailable() {
        try {
            return storage.get(bucket) != null;
        } catch (final Exception e) {

        });

        // Verify hash was reset
        Method resetMethod = findMethod(transport.getClass(), "resetPreauthHash");
        if (resetMethod != null) {
            // Verify the reset method exists
            assertNotNull(resetMethod);
        }
    }

    /**
     * Test that getPreauthIntegrityHash returns a defensive copy
     */
    @Test

        File localFile = new File(localRepo.getBasedir(), localRepo.pathOf(artifact));

        artifact.setFile(localFile);

        if (!localFile.exists()) {
            if (request.getRemoteRepositories().isEmpty()) {
                throw new IOException(localFile + " does not exist and no remote repositories are configured");
            }

            ArtifactRepository remoteRepo = request.getRemoteRepositories().get(0);

        passwordField.setAccessible(true);

        // Verify password exists before wipe
        char[] passwordBefore = (char[]) passwordField.get(authenticator);
        assertNotNull(passwordBefore, "Password should exist before wipe");
        assertArrayEquals(testPassword.toCharArray(), passwordBefore, "Password should match before wipe");

        // Wipe the password