'This method returns the order of the Weyl group.
For types A, B, C, D, and E the order depends on
the rank of the Lie algebra.  For types F and G,
the order is fixed.
Examples
>>> from sympy.liealgebras.weyl_group import WeylGroup
>>> c = WeylGroup("D4")
>>> c.group_order()
192.0'

def group_order(self):

    n = self.cartan_type.rank()
    if (self.cartan_type.series == 'A'):
        return fac((n + 1))
    if ((self.cartan_type.series == 'B') or (self.cartan_type.series == 'C')):
        return (fac(n) * (2 ** n))
    if (self.cartan_type.series == 'D'):
        return (fac(n) * (2 ** (n - 1)))
    if (self.cartan_type.series == 'E'):
        if (n == 6):
            return 51840
        if (n == 7):
            return 2903040
        if (n == 8):
            return 696729600
    if (self.cartan_type.series == 'F'):
        return 1152
    if (self.cartan_type.series == 'G'):
        return 12
