how to get the general formula of SHA-TATE GROUP?

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how to get SHA general formula by parametrization a1, a2, a3, a4, a6,no a number

E=EllipticCurve([0,1]);E;S=E.sha();S

Elliptic Curve defined by y^2 = x^3 + 1 over Rational Field
Tate-Shafarevich group for the Elliptic Curve defined by y^2 = x^3 + 1
over Rational Field

 R.<a1,a2,a3,a4,a6>=QQ[];show(R);E=EllipticCurve([a1,a2,a3,a4,a6]);show(E)

Multivariate Polynomial Ring in a1, a2, a3, a4, a6 over Rational Field
Elliptic Curve defined by y^2 + a1*x*y + a3*y = x^3 + a2*x^2 + a4*x + a6
over Multivariate Polynomial Ring in a1, a2, a3, a4, a6 over Rational
Field

S=E.sha();S

Traceback (click to the left of this block for traceback)
...
AttributeError: 'EllipticCurve_generic_with_category' object has no
attribute 'sha'