This function returns a table that contains the signature of a model. The signature of a model is the set of all input data fields which appear in the model's internal equations and whose values are therefore needed to apply the model. For each signature field, its importance for the model may also be contained in the table. It replaces and completes the following methods or functions: DM_getClasMdlSpec, DM_getClusMdlSpec, DM_getRegMdlSpec, DM_getNumColumns, DM_getFldName, DM_getFldType.