function get_attribute_expression(attribute) {
	return Array.isArray(attribute.value)
		? /** @type {AST.ExpressionTag} */ (attribute.value[0]).expression
		: attribute.value.expression;
}
Returns the single attribute expression node.
In Svelte 5, this also includes a single expression node wrapped in an array.
TODO change that in a future version
@param { AST.Attribute & { value: [AST.ExpressionTag] | AST.ExpressionTag }} attribute
@returns {ESTree.Expression}