'Returns the label (Integer or integer expression) of the Idx object.
Examples
>>> from sympy import Idx, Symbol
>>> x = Symbol(\'x\', integer=True)
>>> Idx(x).label
x
>>> j = Symbol(\'j\', integer=True)
>>> Idx(j).label
j
>>> Idx(j + 1).label
j + 1'

@property
def label(self):

    return self.args[0]
