Distinguish between a property that have animated keyframes and markers property

Hello;

I'm trying to make a portion of a script that allows me to shift the keyframes of an animated property of layer according to a new value.

I implemented a recursive function that cycles through all the properties of a layer and add a condition to check if that property has keyframes (animated), however the issue now is that this condition doesn't exclude layers Markers.

function dumpPropTree(rootObj, nestingLevel) 
    {  
    var countProps = rootObj.numProperties;
    for (var propIndex=1; propIndex <= countProps; propIndex++) 
        {
            var prop = rootObj.property(propIndex);
            if (prop.numKeys > 0 && prop.canVaryOverTime==true)
                {
                            //var a=collectKeyframes(prop1);
                            //var b=transferKeyframes(prop1, a);
                            alert (prop.name);
                    }
            if (prop.numProperties > 0)
                        dumpPropTree(prop, nestingLevel+1);
                }
    }
//**************************************************************************************************************************************
function shiftAllKeyFrames (t, oldDuration, newDuration)
    {
            var layersNum=t.numLayers;
            for (var i=1; i<=layersNum; i++)
                {
                    var currentLayer = t.layer(i);
                    dumpPropTree(currentLayer, 0);
                }
        }

if (prop.numKeys > 0 && prop.canVaryOverTime==true)

I thought that adding "canVaryOverTime" will solve this issue.

However, this condition doesn't exclude the Maker property.

I searched a lot, but I didn't find anything resourceful to this situation.

So, what should I add to exclude Markers property.

Thank you in advance.