def arbitrary_point(self, parameter='t'):
        """A parameterized point on the ellipse.

        Parameters
        ==========

        parameter : str, optional
            Default value is 't'.

        Returns
        =======

        arbitrary_point : Point

        Raises
        ======

        ValueError
            When `parameter` already appears in the functions.

        See Also
        ========

        sympy.geometry.point.Point

        Examples
        ========

        >>> from sympy import Point, Ellipse
        >>> e1 = Ellipse(Point(0, 0), 3, 2)
        >>> e1.arbitrary_point()
        Point2D(3*cos(t), 2*sin(t))

        """
        t = _symbol(parameter)
        if (f.name for f in self.free_symbols) in t.name:
            raise ValueError(filldedent('Symbol %s already appears in object '
                'and cannot be used as a parameter.' % t.name))
        return Point(self.center.x + self.hradius*cos(t),
                     self.center.y + self.vradius*sin(t))
dataset/ETHPy150Open sympy/sympy/sympy/geometry/ellipse.py/Ellipse.arbitrary_point/swapped operands of `in`