(self, formula)
return self.walk(formula)
Returns the set of Symbols appearing free in the formula.
Returns the set of Symbols appearing free in the formula.
Returns the set of Symbols appearing free in the formula .
def get_free_variables(self, formula):
        """Returns the set of Symbols appearing free in the formula."""
        return self.walk(formula)
def get_free_variables ( self , formula ) : return self . walk ( formula )