Solving a univariate polynomial after Grobner basis

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I'm working on a simple exercise of homotopy continuation in sage maths as follows.

# Import necessary modules
from sage.all import *

# Define the polynomial ring
R.<x, y, t> = PolynomialRing(QQ, order='lex')

# Define the target system and start system as polynomials
f = [x^2 + 4*y^2 - 4, 2*y^2 - x]  # target system
g = [x^2 - 1, y^2 - 1]            # start system

# Define the homotopy
h = [t*fi + (1-t)*gi for fi, gi in zip(f, g)]

# Expand the homotopy
eh = [expand(hi) for hi in h]

# Compute the Jacobian matrix
jh = matrix([[diff(ehi, xi) for xi in [x, y]] for ehi in eh])

# Discriminant system: homotopy equations + determinant of the Jacobian matrix
sys = eh + [jh.det()]

# Convert the system to polynomials in the polynomial ring
sys_polynomials = [R(equation) for equation in sys]

# Compute the Groebner basis with lexicographic ordering
I = Ideal(sys_polynomials)
gb = I.groebner_basis()

# Extract the discriminant polynomial
discriminant_poly = gb[-1]

# Solve discriminant_poly
discriminant_poly.roots()

My question

I'm getting the following error. could someone tell me how to solve this polynomial using a SageMaths function?

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In [1], line 34
     31 discriminant_poly = gb[-Integer(1)]
     33 # Solve discriminant_poly
---> 34 discriminant_poly.roots()

File /home/sc_serv/sage/src/sage/structure/element.pyx:489, in sage.structure.element.Element.__getattr__()
    487         AttributeError: 'LeftZeroSemigroup_with_category.element_class' object has no attribute 'blah_blah'...
    488     """
--> 489     return self.getattr_from_category(name)
    490 
    491 cdef getattr_from_category(self, name) noexcept:

File /home/sc_serv/sage/src/sage/structure/element.pyx:502, in sage.structure.element.Element.getattr_from_category()
    500     else:
    501         cls = P._abstract_element_class
--> 502     return getattr_from_other_class(self, cls, name)
    503 
    504 def __dir__(self):

File /home/sc_serv/sage/src/sage/cpython/getattr.pyx:362, in sage.cpython.getattr.getattr_from_other_class()
    360     dummy_error_message.cls = type(self)
    361     dummy_error_message.name = name
--> 362     raise AttributeError(dummy_error_message)
    363 attribute = <object>attr
    364 # Check for a descriptor (__get__ in Python)

AttributeError: 'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular' object has no attribute 'roots'