'It is possible to draw the line only for pair of continuous attrs'

def test_regression_line(self):

    self.send_signal(self.widget.Inputs.data, self.data)
    self.assertTrue(self.widget.cb_reg_line.isEnabled())
    self.assertIsNone(self.widget.graph.reg_line_item)
    self.widget.cb_reg_line.setChecked(True)
    self.assertIsNotNone(self.widget.graph.reg_line_item)
    self.widget.cb_attr_y.activated.emit(4)
    self.widget.cb_attr_y.setCurrentIndex(4)
    self.assertFalse(self.widget.cb_reg_line.isEnabled())
    self.assertIsNone(self.widget.graph.reg_line_item)
