blueprint change: worker indexing functionregister

[YunchuWang]

Description

Fixes #

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PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[codecov]

Codecov Report

Merging #1065 (4593265) into dev (f3ec8a9) will not change coverage.
The diff coverage is 75.00%.

@@           Coverage Diff           @@
##              dev    #1065   +/-   ##
=======================================
  Coverage   83.46%   83.46%           
=======================================
  Files          33       33           
  Lines        1778     1778           
  Branches      282      282           
=======================================
  Hits         1484     1484           
  Misses        230      230           
  Partials       64       64           

Flag	Coverage Δ
unittests	83.46% <75.00%> (ø)

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Impacted Files	Coverage Δ
azure_functions_worker/loader.py	84.52% <75.00%> (ø)

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[vrdmr]

LGTM.

One small comment only for future.