[#59] Add remaining expressions to Indigo

Description

Some expressions that are present in Lorentz are missing in Indigo. This MR resolves it.

Related issue(s)

Resolves #59 (closed)

✅ Checklist for your Merge Request

Related changes (conditional)

• Tests (see short guidelines)

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

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    • Haddock
    • docs/
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