matplotlib.pyplot.fill_between(x, y1, y2=0, where=None, interpolate=False, step=None, *, data=None, **kwargs)
Parameters : 
x: array (length N)
The x coordinates of the nodes defining the curves.

y1: array (length N) or scalar
The y coordinates of the nodes defining the first curve.

y2: array (length N) or scalar, default: 0
The y coordinates of the nodes defining the second curve.