QTableWidgetItem Class text = data(Qt::DisplayRole).toString()

I found in some book the statement that the text property of QTableWidgetItem Class is equivalent to calling data(Qt::DisplayRole).toString(). My question is about assistant: how do I check the statement using assistant? I found no explanations of text and roles in QTableWidgetItem Class and no connection to Qt::DisplayRole. Should I expect that many parts of assistant can not be understood regardless how carefully they are read? I mean, some classes are not completely explained in the documentation?