function findOpeningParenOfParams(node) {
			const tokenBeforeParams = sourceCode.getTokenBefore(node.params[0]);

			if (
				tokenBeforeParams &&
				astUtils.isOpeningParenToken(tokenBeforeParams) &&
				node.range[0] <= tokenBeforeParams.range[0]
			) {
				return tokenBeforeParams;
			}

			return null;
		}
Finds opening paren of parameters for the given arrow function, if it exists.
It is assumed that the given arrow function has exactly one parameter.
@param {ASTNode} node `ArrowFunctionExpression` node.
@returns {Token|null} the opening paren, or `null` if the given arrow function doesn't have parens of parameters.