Child class with different signatures, how to reasonable resolve it without breaking the code?

I am implementing machine learning algorithms from scratch using python. I have a base class called BaseEstimator with the following structure:

from __future__ import annotations

from typing import Optional, TypeVar
import numpy as np
from abc import ABC, abstractmethod

T = TypeVar("T", np.ndarray, torch.Tensor)


class BaseEstimator(ABC):
    """Base Abstract Class for Estimators."""

    @abstractmethod
    def fit(self, X: T, y: Optional[T] = None) -> BaseEstimator:
        """Fit the model according to the given training data.

        Parameters
        ----------
        X : array-like, shape (n_samples, n_features)
            Training vector, where n_samples is the number of samples and
            n_features is the number of features.

        y : array-like, shape (n_samples,) or (n_samples, n_outputs), optional
            Target relative to X for classification or regression;
            None for unsupervised learning.

        Returns
        -------
        self : object
            Returns self.
        """

    @abstractmethod
    def predict(self, X: T) -> T:
        """Predict class labels for samples in X.

        Parameters
        ----------
        X : array-like, shape (n_samples, n_features)
            Samples.

        Returns
        -------
        C : array, shape (n_samples,)
            Predicted class label per sample.
        """

class KMeans(BaseEstimator):

    def fit(X: T) -> BaseEstimator:
        ...

    def predict(X: T) -> T:
        ...


class LogisticRegression(BaseEstimator):
    def fit(X: T, y: Optional[T] = None) -> BaseEstimator:
        ...

    def predict(X: T) -> T:
        ...

Now when I implemented the base class, I did not plan properly, some algorithms such as KMeans are unsupervised and hence do not need y at all in fit. Now a quick fix I thought of is to type hint y as Optional, so that it can be None, is that okay? In that case, in KMeans' fit method, I will also have to include the y: Optional[T] = None, which will never be used.