Error on Metadata type when I try to do POST

Question

I have this code:

function insertuser(obj){
        var listID = obj.getAttribute('data-listid'),
            itemID = obj.getAttribute('data-itemid'),
            URLID = obj.getAttribute('data-itemurl');

        var UserId = _spPageContextInfo.userId;

        var returl = URLID;
        var res1 = returl.substring(0,62);
        var REGEX = /.*\/Normativo\/(.+?)\/.*/;
        var res2 = returl.replace(REGEX, "$1");

        var res3 = res1.concat(res2);

        jQuery.ajax({
            url: res3 + "/_api/web/lists('" + listID + "')/items('" + itemID +"')?$select=ID,Title,QuemLeu/Id&$expand=QuemLeu",
            method: "GET",
            headers: {
                "Accept": "application/json; odata=verbose" 
            },
            success: function (data) {

                var userIdArray = [];
                if(data.d){
                    if(data.d.QuemLeu.results) {
                        for (var i = 0; i < data.d.QuemLeu.results.length; i++) {
                            userIdArray.push(data.d.QuemLeu.results[i].Id);
                        }
                    }
                }
                userIdArray.push(UserId);
                var fields = {
                    "__metadata": { 'type': "SP.Data.PaginasItem"},
                    "QuemLeuId": {"results": userIdArray  }
                }
                updateItem(fields);
            }, 
            error: function (error) {
                console.log(error);
            }
        });


        function updateItem(fields) {
            jQuery.ajax({  
                url: res3 + "/_api/web/lists('" + listID + "')/items('" + itemID +"')",  
                type: "POST",
                    data: JSON.stringify(fields),  
                    contentType: "application/json;odata=verbose",
                    headers: {  
                        "Accept": "application/json;odata=verbose",
                        "X-RequestDigest" : document.getElementById("__REQUESTDIGEST").value,
                        "X-HTTP-Method": "MERGE",
                        "If-Match": "*"  
                    },  
                success: function(data) {  
                   console.log("OK POST");
                   alert("OK POST");
                },  
                error: function(error) {  
                    console.log("ERRO POST");
                    console.log(JSON.stringify(error));  
                }  
            });
        }
    }

When executing gives me this error:

This code is being used for items that are stored on the Sharepoint Pages and in a document library. The code works correctly for the Pages list, but for the document library does not. I’ve seen Listitementitytypefullname from the Pages list and it’s SP.Data.Paginasitem but it seems that Listitementitytypefullname does not work for document libraries. What I must do to make it work for both Pages and Document Library?