Create a figure instance.

    :params width: figure width
    :params height: figure height

def create_figure(width=20, height=10):
    """Create a figure instance.

    :params width: figure width
    :params height: figure height
    """
    figure = plt.figure(figsize=(width, height))
    axis = figure.add_subplot(1, 1, 1)
    return figure, axis