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, optional, default: 0
The y coordinates of the nodes defining the second curve.
 where : array of bool (length N), optional, default: None
Define where to exclude some horizontal regions from being
filled. The filled regions are defined by the coordinates
x[where] . More precisely, fill between x[i] and x[i+1]
if where[i] and where[i+1] . Note that this definition implies
that an isolated True value between two False values in
where will not result in filling. Both sides of the True
position remain unfilled due to the adjacent False values.
 interpolate : bool, optional
This option is only relvant if where is used and the two curves
are crossing each other.
Semantically, where is often used for y1 > y2 or similar.
By default, the nodes of the polygon defining the filled region
will only be placed at the positions in the x array. Such a
polygon cannot describe the above semantics close to the
intersection. The xsections containing the intersecion are
simply clipped.
Setting interpolate to True will calculate the actual
interscection point and extend the filled region up to this point.
 step : {‘pre’, ‘post’, ‘mid’}, optional
Define step if the filling should be a step function,
i.e. constant in between x. The value determines where the
step will occur:
 ‘pre’: The y value is continued constantly to the left from
every x position, i.e. the interval
(x[i1], x[i]] has the
value y[i] .
 ‘post’: The y value is continued constantly to the right from
every x position, i.e. the interval
[x[i], x[i+1]) has the
value y[i] .
 ‘mid’: Steps occur halfway between the x positions.

Other Parameters: 
 **kwargs
All other keyword arguments are passed on to PolyCollection .
They control the Polygon properties:
Property 
Description 
agg_filter 
a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array 
alpha 
float or None 
animated 
bool 
antialiased or antialiaseds 
Boolean or sequence of booleans 
array 
ndarray 
capstyle 
unknown 
clim 
a length 2 sequence of floats; may be overridden in methods that have vmin and vmax kwargs. 
clip_box 
a Bbox instance 
clip_on 
bool 
clip_path 
[(Path , Transform )  Patch  None] 
cmap 
a colormap or registered colormap name 
color 
matplotlib color arg or sequence of rgba tuples 
contains 
a callable function 
edgecolor or edgecolors 
matplotlib color spec or sequence of specs 
facecolor or facecolors 
matplotlib color spec or sequence of specs 
figure 
a Figure instance 
gid 
an id string 
hatch 
[ ‘/’  ‘'  ‘’  ‘‘  ‘+’  ‘x’  ‘o’  ‘O’  ‘.’  ‘*’ ] 
joinstyle 
unknown 
label 
object 
linestyle or dashes or linestyles 
[‘solid’  ‘dashed’, ‘dashdot’, ‘dotted’  (offset, onoffdashseq)  ''  ''  '.'  ':'  'None'  ' '  '' ] 
linewidth or linewidths or lw 
float or sequence of floats 
norm 
Normalize 
offset_position 
[ ‘screen’  ‘data’ ] 
offsets 
float or sequence of floats 
path_effects 
AbstractPathEffect 
picker 
[None  bool  float  callable] 
pickradius 
float distance in points 
rasterized 
bool or None 
sketch_params 
(scale: float, length: float, randomness: float) 
snap 
bool or None 
transform 
Transform 
url 
a url string 
urls 
List[str] or None 
visible 
bool 
zorder 
float 
