'Return the coordinates which the wavefunction depends on
Examples
>>> from sympy.physics.quantum.state import Wavefunction
>>> from sympy import symbols
>>> x,y = symbols(\'x,y\')
>>> f = Wavefunction(x*y, x, y)
>>> f.variables
(x, y)
>>> g = Wavefunction(x*y, x)
>>> g.variables
(x,)'

@property
def variables(self):

    var = [(g[0] if isinstance(g, Tuple) else g) for g in self._args[1:]]
    return tuple(var)
