How to use the gstools.covmodel.base.CovModel function in gstools

def __eq__(self, other):
        """Compare CovModels."""
        if not isinstance(other, CovModel):
            return False
        # prevent attribute error in opt_arg if the are not equal
        if set(self.opt_arg) != set(other.opt_arg):
            return False
        # prevent dim error in anis and angles
        if self.dim != other.dim:
            return False
        equal = True
        equal &= self.name == other.name
        equal &= np.isclose(self.var, other.var)
        equal &= np.isclose(self.var_raw, other.var_raw)  # ?! needless?
        equal &= np.isclose(self.nugget, other.nugget)
        equal &= np.isclose(self.len_scale, other.len_scale)
        equal &= np.all(np.isclose(self.anis, other.anis))
        equal &= np.all(np.isclose(self.angles, other.angles))
        for opt in self.opt_arg:

# modify the docstrings ###############################################

        # class docstring gets attributes added
        if cls.__doc__ is None:
            cls.__doc__ = (
                "User defined GSTools Covariance-Model "
                + CovModel.__doc__[44:-296]
            )
        else:
            cls.__doc__ += CovModel.__doc__[44:-296]
        # overridden functions get standard doc if no new doc was created
        ignore = ["__", "variogram", "covariance", "correlation"]
        for attr in cls.__dict__:
            if any(
                [attr.startswith(ign) for ign in ignore]
            ) or attr not in dir(CovModel):
                continue
            attr_doc = getattr(CovModel, attr).__doc__
            attr_cls = cls.__dict__[attr]
            if attr_cls.__doc__ is None:
                attr_cls.__doc__ = attr_doc

self.reset_seed(self._seed)
            # just update the seed, if its a new one
            elif seed is None or not np.isnan(seed):
                self.seed = seed
        # or just update the seed, when no model is given
        elif model is None and (seed is None or not np.isnan(seed)):
            if isinstance(self._model, CovModel):
                self.seed = seed
            else:
                raise ValueError(
                    "gstools.field.generator.RandMeth: no 'model' given"
                )
        # if the user tries to trick us, we beat him!
        elif model is None and np.isnan(seed):
            if (
                isinstance(self._model, CovModel)
                and self._z_1 is not None
                and self._z_2 is not None
                and self._cov_sample is not None
            ):
                if self.verbose:
                    print("RandMeth.update: Nothing will be done...")
            else:
                raise ValueError(
                    "gstools.field.generator.RandMeth: "
                    + "neither 'model' nor 'seed' given!"
                )
        # wrong model type
        else:
            raise ValueError(
                "gstools.field.generator.RandMeth: 'model' is not an "
                + "instance of 'gstools.CovModel'"

+ cls.__name__
                + "', "
                + "without overriding at least on of the methods "
                + "'variogram', 'covariance' or 'correlation'."
            )

        # modify the docstrings ###############################################

        # class docstring gets attributes added
        if cls.__doc__ is None:
            cls.__doc__ = (
                "User defined GSTools Covariance-Model "
                + CovModel.__doc__[44:-296]
            )
        else:
            cls.__doc__ += CovModel.__doc__[44:-296]
        # overridden functions get standard doc if no new doc was created
        ignore = ["__", "variogram", "covariance", "correlation"]
        for attr in cls.__dict__:
            if any(
                [attr.startswith(ign) for ign in ignore]
            ) or attr not in dir(CovModel):
                continue
            attr_doc = getattr(CovModel, attr).__doc__
            attr_cls = cls.__dict__[attr]
            if attr_cls.__doc__ is None:
                attr_cls.__doc__ = attr_doc

def update(self, model=None, seed=np.nan):
        """Update the model and the seed.

        If model and seed are not different, nothing will be done.

        Parameters
        ----------
        model : :any:`CovModel` or :any:`None`, optional
            covariance model. Default: :any:`None`
        seed : :class:`int` or :any:`None` or :any:`numpy.nan`, optional
            the seed of the random number generator.
            If :any:`None`, a random seed is used. If :any:`numpy.nan`,
            the actual seed will be kept. Default: :any:`numpy.nan`
        """
        # check if a new model is given
        if isinstance(model, CovModel):
            if self.model != model:
                self._model = dcp(model)
                if seed is None or not np.isnan(seed):
                    self.reset_seed(seed)
                else:
                    self.reset_seed(self._seed)
            # just update the seed, if its a new one
            elif seed is None or not np.isnan(seed):
                self.seed = seed
        # or just update the seed, when no model is given
        elif model is None and (seed is None or not np.isnan(seed)):
            if isinstance(self._model, CovModel):
                self.seed = seed
            else:
                raise ValueError(
                    "gstools.field.generator.RandMeth: no 'model' given"

def model(self, model):
        if isinstance(model, CovModel):
            self._model = model
        else:
            raise ValueError(
                "Field: 'model' is not an instance of 'gstools.CovModel'"
            )

# class docstring gets attributes added
        if cls.__doc__ is None:
            cls.__doc__ = (
                "User defined GSTools Covariance-Model "
                + CovModel.__doc__[44:-296]
            )
        else:
            cls.__doc__ += CovModel.__doc__[44:-296]
        # overridden functions get standard doc if no new doc was created
        ignore = ["__", "variogram", "covariance", "correlation"]
        for attr in cls.__dict__:
            if any(
                [attr.startswith(ign) for ign in ignore]
            ) or attr not in dir(CovModel):
                continue
            attr_doc = getattr(CovModel, attr).__doc__
            attr_cls = cls.__dict__[attr]
            if attr_cls.__doc__ is None:
                attr_cls.__doc__ = attr_doc