Handle case where there are multiple label values

[nicwells]

Fixes BlueBrain/nexus#3119

Description

Previously it was assumed there was a single label however there could be several. We now handle the case that there is more than one label.

How has this been tested?

Types of changes

• 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)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added necessary unit and integration tests.
• I have added screenshots (if applicable), in the comment section.

[codecov-commenter]

Codecov Report

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