code: def _are_coordinates_valid(self):
          
          try:
              QgsPointXY(
                  self.x_minimum.value(),
                  self.y_maximum.value())
              QgsPointXY(
                  self.x_maximum.value(),
                  self.y_minimum.value())
          except ValueError:
              return False
  
          return True
docs: Check if the coordinates are valid.
  
          :return: True if coordinates are valid otherwise False.
          :type: bool