Problem with streamline

Hi,

I am having an issue to reproduce one of the animations with streamlines in div_curl.py. I have used the following command:

`python3.7 ./manim.py div_curl.py DefineDivergence -pl -r 540`

The error message is

`
File "/home/manim/manimlib/extract_scene.py", line 155, in main
scene = SceneClass(**scene_kwargs)
File "/home/manim/manimlib/scene/scene.py", line 53, in __init__
self.construct()
File "div_curl.py", line 1459, in construct
self.show_flow()
File "div_curl.py", line 1490, in show_flow
**self.stream_line_config
File "/home/manim/manimlib/mobject/vector_field.py", line 229, in __init__
**self.start_points_generator_config
TypeError: get_start_points() got an unexpected keyword argument 'delta_x'

`
Could you please help me with this?

Thank you,
Raj

此錯誤發生在 manimlib/mobject/vector_field.py 的第229行，其中 get_start_points() 收到一個未預期的關鍵字參數 'delta_x'。檢查 div_curl.py 的第1490行中的 stream_line_config，並與 vector_field.py 中 get_start_points 的簽名進行比較。檢查 'delta_x' 是否為有效參數，或是否需要更新配置。運行特定場景並進行除錯將有助於追蹤不匹配。

由索引模型根據 Issue 內容生成。