'Construct a new Axis.
Args:
axis_min: smallest value on the axis
axis_max: largest value on the axis'

def __init__(self, axis_min=None, axis_max=None):

    self.min = axis_min
    self.max = axis_max
    self.labels = []
    self.label_positions = []
    self.grid_spacing = 0
    self.label_gridlines = False
