`extract_adapters`: plugin docs generation fails when hook is present

[timlehr]

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Bug Report

On the extract_adapters branch there is an issue with the plugin docs generation / tests. If there are hooks with hook scripts in the path, the code doesn't handle them correctly and we get an error:

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ERROR: test_plugin_documentation (test_serialized_schema.PluginDocumentationTester)
Verify that the plugin manifest matches what is checked into the
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Traceback (most recent call last):
  File "/Users/tlehr/dev/OpenTimelineIO/tests/test_serialized_schema.py", line 62, in test_plugin_documentation
    sanitized_paths=True
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/opentimelineio/console/autogen_plugin_documentation.py", line 337, in generate_and_write_documentation_plugins
    sanitized_paths
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/opentimelineio/console/autogen_plugin_documentation.py", line 283, in _manifest_formatted
    if manifest_paths and plug['from manifest'] not in manifest_paths:
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/opentimelineio/core/_core_utils.py", line 223, in __getitem__
    return self.__internal_getitem__(index)
TypeError: __internal_getitem__(): incompatible function arguments. The following argument types are supported:
    1. (self: opentimelineio._otio.AnyVector, index: int) -> object

Invoked with: ['studio_pre_write_hook'], 'from manifest'

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[apetrynet]

Fixed in PR #1644