Generates a layout with the union of all properties of multiple
	figures' layouts

	Parameters:
	-----------
		fig : list(Figures)
			List of Plotly Figures

def get_base_layout(figs):
	"""
	Generates a layout with the union of all properties of multiple
	figures' layouts

	Parameters:
	-----------
		fig : list(Figures)
			List of Plotly Figures
	"""
	layout={}
	for fig in figs:
		if not isinstance(fig,dict):
			fig=fig.to_dict()
		for k,v in list(fig['layout'].items()):
			layout[k]=v
	return layout