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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_shape(kind='line',x=None,y=None,x0=None,y0=None,x1=None,y1=None,span=0,color='red',dash='solid',width=1, 				fillcolor=None,fill=False,opacity=1,xref='x',yref='y'):
 	""" 	Returns a plotly shape 	Parameters: 		kind : string 			Shape kind 				line 				rect 				circle 		x : float 			x values for the shape. 			This assumes x0=x1 		x0 : float 			x0 value for the shape 		x1 : float 			x1 value for the shape 		y : float 			y values for the shape. 			This assumes y0=y1 		y0 : float 			y0 value for the shape 		y1 : float 			y1 value for the shape 		color : string 			color for shape line 		dash : string 			line style 				solid 				dash 				dashdot 				dot 		width : int 			line width 		fillcolor : string 			shape fill color 		fill : bool 			If True then fill shape 			If not fillcolor then the 			line color will be used 		opacity : float [0,1] 			opacity of the fill 		xref : string 			Sets the x coordinate system 			which this object refers to 				'x' 				'paper' 				'x2' etc 		yref : string 			Sets the y coordinate system 			which this object refers to 				'y' 				'paper' 				'y2' etc 	"""

	if x1 is None:
		if x0 is None:
			if x is None:
				xref='paper'
				x0=0
				x1=1
			else:
				x0=x1=x
		else:
			x1=x0
	else:
		x
	if y1 is None:
		if y0 is None:
			if y is None:
				yref='paper'
				y0=0
				y1=1
			else:
				y0=y1=y
		else:
			y1=y0

	shape = {	'x0':x0,
				'y0':y0,
				'x1':x1,
				'y1':y1,
				'line' : {
					'color':normalize(color),
					'width':width,
					'dash':dash
					},
				'xref':xref,
				'yref':yref
				}

	if kind=='line':
		shape['type']='line'

	elif kind=='circle':
		shape['type']='circle'

	elif kind=='rect':
		shape['type']='rect'
	else:
		raise Exception("Invalid or unkown shape type : {0}".format(kind))

	if (fill or fillcolor) and kind!='line':
		fillcolor = color if not fillcolor else fillcolor
		fillcolor=to_rgba(normalize(fillcolor),opacity)
		shape['fillcolor']=fillcolor

	return shape