Plot Function with Default Parameters in Python

`defs` is a list of default values for the parameters of the `plot` function. It is used to specify default values for the parameters that are not provided when calling the function.

For example, if you want to plot a line chart with a blue line and a red line, but you don't want to specify the colors for each line every time you call the function, you can use `defs` to define the default colors:
```
def plot(x, y, color='blue', linestyle='-'):
# ...
defs = {'color': ['blue', 'red']}
# ...
```
Now, when you call the function like this:
```
plot([1, 2, 3], [4, 5, 6])
```
The blue line will be used by default, but you can override the default color by specifying a different color in the `color` parameter:
```
plot([1, 2, 3], [4, 5, 6], color='red')
```
This way, you only need to specify the default values for the parameters that are not required every time you call the function.