tooltip = None
for testedTooltip in dataviz.Details.Items:
    testedTooltipType = testedTooltip.GetType()
	if(testedTooltipType == 'Spotfire.Dxp.Application.Visuals.ExpressionDetailItem' and	testedTooltip.Expression == jsonParam['expression']):
        tooltip = testedTooltip
        break
if(tooltip == None):
    tooltip = dataviz.Details.Items.AddExpression(jsonParam['expression'])
if(jsonParam['renderer']['type'] != None):
    rendererType = getValueRendererType(jsonParam['renderer']['type'])
    tooltipRendererSettings = tooltip.SetValueRenderer(rendererType)
if(jsonParam['renderer']['type'] == 'Image from URL'):
    if(jsonParam['renderer']['urlTemplate'] != None):
        tooltipRendererSettings.UrlTemplate = jsonParam['renderer']['urlTemplate']
    if(jsonParam['size'] != None):
        tooltip.ImageSize = jsonParam['size']
