function checkFunctionsBlockStatement(node) {
      if (astUtil.isFunctionLikeExpression(node)) {
        if (node.body.type === 'BlockStatement') {
          getReturnStatements(node.body)
            .filter((returnStatement) => returnStatement && returnStatement.argument)
            .forEach((returnStatement) => {
              checkIteratorElement(returnStatement.argument);
            });
        }
      }
    }
Checks if the given node is a function expression or arrow function,
and checks if there is a missing key prop in return statement's arguments
@param {ASTNode} node