Bugfix for similarity return types

[richardpaulhudson]

Description

In the past, calls to Lexeme.similarity(), Span.similarity() and Token.similarity() have returned inconsistent return types: depending on whether or not matrix multiplication was performed to determine the similarity and whether or not Numpy (CPU) or Cupy (GPU) was in use, the return value could be a native Python float, a Numpy float or a Cupy array. This pull request duplicates the pre-existing behaviour of Doc.similarity() and ensures that all return values are native floats.

Types of change

Bug fix

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.

[adrianeboyd]

@explosion-bot please test_gpu

[explosion-bot]

🪁 Successfully triggered build on Buildkite

URL: https://buildkite.com/explosion-ai/spacy-gpu-test-suite/builds/53

[svlandeg]

Good catch! And it looks like the test suite is also happy on GPU so we can go ahead and merge this :-)