Moved check out of the loop to avoid quadratic runtime.

[ChristopherBrix]

Description

The test that verifies that all label ids are non-negative is not influenced by the loop, so it can be performed once at the beginning. This avoids a quadratic runtime, which has a high impact on execution time for very long sequences.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Tests

• official/nlp/data/tagging_data_lib_test.py

Checklist

• I have signed the Contributor License Agreement.
• I have read guidelines for pull request.
• My code follows the coding guidelines.
• I have performed a self code review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.

Code owners: @saberkun @chengithuber @lehougoogle @rachellj218 @jaeyounkim

CC: My intern host sundermeyer@google.com and co-host fhartmann@google.com

[saberkun]

Thank you!