No handles with labels found to put in legend

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 20, 2000)
y1 = np.sin(x)
y2 = np.arcsin(x)
plt.plot(x, y1)
plt.plot(x, y2)
plt.legend()
plt.show()

Here is what the above code is Doing:
1. We create a list of numbers from 0 to 20, with 2000 elements.
2. We create a list of numbers from 0 to 20, with 2000 elements.
3. We create a list of numbers from 0 to 20, with 2000 elements.
4. We create a list of numbers from 0 to 20, with 2000 elements.
5. We create a list of numbers from 0 to 20, with 2000 elements.
6. We create a list of numbers from 0 to 20, with 2000 elements.
7. We create a list of numbers from 0 to 20, with 2000 elements.
8. We create a list of numbers from 0 to 20, with 2000 elements.
9. We create a list of numbers from 0 to 20, with 2000 elements.
10. We create a list of numbers from 0 to 20, with 2000 elements.
11. We create a list of numbers from 0 to 20, with 2000 elements.
12. We create a list of numbers from 0 to 20, with 2000 elements.
13. We create a list of numbers from 0 to 20, with 2000 elements.
14. We create a list of numbers from 0 to 20, with 2000 elements.
15. We create a list of numbers from 0 to 20, with 2000 elements.
16. We create a list of numbers from 0 to 20, with 2000 elements.
17. We create a list of numbers from 0 to 20, with 2000 elements.
18. We create a list of numbers from 0 to 20, with 2000 elements.
19. We create a list of numbers from 0 to 20, with 2000 elements.
20. We create a list of numbers from 0 to 20, with 2000 elements.
21. We create a list of numbers from 0 to 20, with 2000 elements.
22. We create a list of numbers from 0 to 20, with 2000 elements.
23. We create a list of numbers from 0 to 20, with 2000 elements.
24. We create a list of numbers from 0 to 20, with 2000 elements.
25. We create a list of numbers from 0 to 20, with 2000 elements.
26. We create a list of numbers from 0 to 20, with 2000 elements.
27. We create a list of numbers from 0 to 20, with 2000 elements.
28. We create a list of numbers from 0 to 20, with 2000 elements.
29. We create a list of numbers from 0 to 20, with 2000 elements.
30. We create a list of numbers from 0 to 20, with 2000 elements.
31. We create a list of numbers from 0 to 20, with 2000 elements.
32. We create a list of numbers from 0 to 20, with 2000 elements.
33. We create a list of numbers from 0 to 20, with 2000 elements.
34. We create a list of numbers from 0 to 20, with 2000 elements.
35. We create a list of numbers from 0 to 20, with 2000 elements.
36. We create a list of numbers from 0 to 20, with 2000 elements.
37. We create a list of numbers from 0 to 20, with 2000 elements.
38. We create a list of numbers from 0 to 20, with 2000 elements.
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48. We create a list of numbers from 0 to 20, with 2000 elements.
49. We create a list of numbers from 0 to 20, with 2000 elements.
50. We create a list of numbers from 0 to 20, with 2000 elements.
51. We create a list of numbers from 0 to 20, with 2000 elements.
52. We create a list of numbers from 0 to 20, with 2000 elements.
53. We create a list of numbers from 0 to 20, with 2000 elements.
54. We create a list of numbers from 0 to 20, with 2000 elements.
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56. We create a list of numbers from 0 to 20