'Checks to see if the permutation contains only one number and is
thus the only possible permutation of this set of numbers
Examples
>>> from sympy.combinatorics import Permutation
>>> Permutation([0]).is_Singleton
True
>>> Permutation([0, 1]).is_Singleton
False
See Also
is_Empty'

@property
def is_Singleton(self):

    return (self.size == 1)
