But we want to be able to parameterize that fixed content.

## A "callable" instance

In Python there's a way to make an instance of a class a "callable".

Not the class itself (which is already a callable), but an instance of that class.

To do that, we declare a method `__call__`:

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[12] *}

                    checkArgument(elements.length == 1);
                    return Sets.union(Sets.<String>newHashSet(elements), newHashSet(elements));
                  }
                })
            .named("singleton U itself")
            .withFeatures(CollectionSize.ONE, CollectionFeature.ALLOWS_NULL_VALUES)
            .createTestSuite());

    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {

                    checkArgument(elements.length == 1);
                    return Sets.union(Sets.<String>newHashSet(elements), newHashSet(elements));
                  }
                })
            .named("singleton U itself")
            .withFeatures(CollectionSize.ONE, CollectionFeature.ALLOWS_NULL_VALUES)
            .createTestSuite());

    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {

    assertThrows(UnsupportedOperationException.class, () -> separated.withSeparator("$", 4));
  }

  public void testBase64() {
    // The following test vectors are specified in RFC 4648 itself
    testEncodingWithSeparators(base64(), "", "");
    testEncodingWithSeparators(base64(), "f", "Zg==");
    testEncodingWithSeparators(base64(), "fo", "Zm8=");
    testEncodingWithSeparators(base64(), "foo", "Zm9v");

   *     the {@link ExecutionException} thrown by {@code input.get()} or, if {@code get()} throws a
   *     different kind of exception, that exception itself. To avoid hiding bugs and other
   *     unrecoverable errors, callers should prefer more specific types, avoiding {@code
   *     Throwable.class} in particular.

Here's where we are using the same OAuth2 scheme we created before, declaring it as a dependency: `oauth2_scheme`.

Because this dependency function doesn't have any scope requirements itself, we can use `Depends` with `oauth2_scheme`, we don't have to use `Security` when we don't need to specify security scopes.

We also declare a special parameter of type `SecurityScopes`, imported from `fastapi.security`.

  <artifactId>testinvalidpom</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <description>
    This will test if the module validator recognized that this
    dependency is the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testinvalidpom</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>

  <artifactId>testvalidpom</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <description>
    This will test if the module validator recognized that this dependency with classifier
    is not the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testvalidpom</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <classifier>linux</classifier>

    assertThrows(UnsupportedOperationException.class, () -> separated.withSeparator("$", 4));
  }

  public void testBase64() {
    // The following test vectors are specified in RFC 4648 itself
    testEncodingWithSeparators(base64(), "", "");
    testEncodingWithSeparators(base64(), "f", "Zg==");
    testEncodingWithSeparators(base64(), "fo", "Zm8=");
    testEncodingWithSeparators(base64(), "foo", "Zm9v");

  }

  /** Test proper handling of case where an object is not equal to itself */
  public void testNonReflexiveEquals() {
    Object obj = new NonReflexiveObject();
    equalsTester.addEqualityGroup(obj);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, obj + " must be Object#equals to itself");
      return;
    }
    fail("Should get non-reflexive error");