Class initialiser

[Jday7879]

Proposed Changes

Related Issues

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• Fixes #

Pre-requisites

This section may not be fully required if the branch is not merging into main.
Please indicate items that aren't necessary and why, with comments around incomplete checks.

• Version number has been incremented, according to SemVer
• Changelog has been updated, listing changes to this version. Use the keep a changelog format
• New features are tested
• New features are documented using the numpydoc docstring format
• Other relevant package documentation is updated
• For new functionality, examples are included in the docs or a feature request has
  been made for it/them
• Required workflows and pre-commits succeed