I am trying to calculate an integral, plot it then highlights the area below it. I managed to find some code that uses the Polygon function, that is giving me an error. 

Below I provide some of the code. 

```
a = 0.5 # left integration limit 
b = 9.5  # right integration limit
Ix = np.linspace(a, b)  
Iy = f(Ix) # Integration function values

verts = [(a, 0)] + list(zip(Ix, Iy)) + [(b, 0)]
poly = Polygon(verts, facecolor='0.7', edgecolor='0.5')

```

the code is giving me the following error,

```
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-9-0113439d2980> in <module>()
      5 
      6 verts = [(a, 0)] + list(zip(Ix, Iy)) + [(b, 0)]
----> 7 poly = Polygon(verts, facecolor='0.7', edgecolor='0.5')

TypeError: __init__() got an unexpected keyword argument 'facecolor'

```

I have tried to look at the shapely user manual <https://shapely.readthedocs.io/en/latest/manual.html> but could not figure out a solution. 

I also found similar errors but this was regarding matplotlib.

Sorry if this is a simple question, I am new to python.