This may seem like a redundant command, but every time I want to negate isEqualTo I find myself going back to the start of an expression to put an `!` and then putting parentheses around it.
But having a command that already returns the negated value is much more convenient.
`_a notEqualTo _b` which would be identical to `!(_a isEqualTo _b)`
This also makes more sense, because we already have:
`==` and `!=`