There is a useless line in the _Quiver class definition

[empet]

In the _Quiver class definition (more precisely within the body of one of its methods) there is a useless line https://github.com/plotly/plotly.py/blob/master/packages/python/plotly/plotly/figure_factory/_quiver.py#L257 which just leads to repeating the calculations of the elements in the four lists under the for loop:

for index in range(len(self.end_x)):
    point1_x = [i - j * self.scaleratio for i, j in zip(self.end_x, seg1_x)]
    point1_y = [i - j for i, j in zip(self.end_y, seg1_y)]
    point2_x = [i - j * self.scaleratio for i, j in zip(self.end_x, seg2_x)]
    point2_y = [i - j for i, j in zip(self.end_y, seg2_y)]

The for line must be removed and the next four lines moved a tab at left.