'The subplot will occupy the num1-th cell of the given
gridspec.  If num2 is provided, the subplot will span between
num1-th cell and num2-th cell.
The index stars from 0.'

def __init__(self, gridspec, num1, num2=None):

    (rows, cols) = gridspec.get_geometry()
    total = (rows * cols)
    self._gridspec = gridspec
    self.num1 = num1
    self.num2 = num2
