Fix for namespaces issue

[brendanjohnharris]

Overview:

Conflicting namespaces for ecephys files (neuropixels nwb files) mean that EcephysSessions and BehaviourEcephysSessions cannot be imported simultaneously. Foregoing manual namespace loading in the NwbApi and relying on loading fromt he nwb files themselves seems to fix this.

Addresses:

Addresses #2713

Type of Fix:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing
  functionality to not work as expected)
• Documentation Change

Changes:

• Delete lines that load a conflicting namespace in the nwb_api file and the ecephys_nwb_session_api` file
• Set the NwbApi to load namespaces from nwb files

Validation:

Screenshots:

Unit Tests:

Script to reproduce error and fix:

Configuration details:

Checklist

• My code follows
  Allen Institute Contribution Guidelines
• My code is unit tested and does not decrease test coverage
• I have performed a self review of my own code
• My code is well-documented, and the docstrings conform to
  Numpy Standards
• I have updated the documentation of the repository where
  appropriate
• The header on my commit includes the issue number
• My Pull Request has the latest AllenSDK release candidate branch
  rc/x.y.z as its merge target
• My code passes all AllenSDK tests

Notes:

[morriscb]

Hi @brendanjohnharris. Thanks for fixing this issue and apologies for the delay in getting to the PR. The change looks good as far as I can tell, but we'll wait for the unittests to complete for before merging. If you have a sec would you mind fixing the two small linting issues in the file? I know this isn't code you touched, the linter is set to run only on changed files so it picked up previous linting error from before the repo had automatic linting. Thanks!

allensdk/brain_observatory/nwb/nwb_api.py:1:1: F401 'pathlib.Path' imported but unused
allensdk/brain_observatory/nwb/nwb_api.py:27:80: E501 line too long (82 > 79 characters)