* The names of the output properties.
         * <p>
         * No duplicate values.
         * Ordered lexicographically.
         * Never empty.
         */
        @Nullable
        List<String> getOutputPropertyNames();
    }

                .map(ImplementationSnapshot::getClassIdentifier)
                .collect(Collectors.toList())
            )
            .orElse(null);
    }

    @Nullable
    public List<String> getOutputPropertyNames() {
        return getBeforeExecutionState()
            .map(BeforeExecutionState::getOutputFileLocationSnapshots)
            .map(ImmutableSortedMap::keySet)

         * <p>
         * No duplicate values.
         * Ordered lexicographically.
         * Never empty.
         */
        @Nullable
        List<String> getOutputPropertyNames();

    }

    private SnapshotTaskInputsBuildOperationType() {
    }