docs: def _internal_add(self, other):
          """ Used for specifing addition methods for
             __add__, __iadd__, __radd__
          """
          if hasattr(other, "datatype"):
              if other.datatype == "xsd:decimal":
                  rtn_val = self.value + Decimal(str(other.value))
              else:
                  rtn_val = self.value + Decimal(str(other.value))
          else:
              rtn_val = self.value + Decimal(str(other))
          return XsdDecimal(str(float(rtn_val)))