def validate(self, require_all=True, scale='colors'):
        """Validate the visualization contents.

        Parameters
        ----------
        require_all : boolean, default True
            If True (default), then all fields ``data``, ``scales``,
            ``axes``, and ``marks`` must be defined. The user is allowed to
            disable this if the intent is to define the elements
            client-side.

        If the contents of the visualization are not valid Vega, then a
        :class:`ValidationError` is raised.
        """
        super(self.__class__, self).validate()
        required_attribs = ('data', 'scales', 'axes', 'marks')
        for elem in required_attribs:
            attr = getattr(self, elem)
            if attr:
                # Validate each element of the sets of data, etc
                for entry in attr:
                    entry.validate()
                names = [a.name for a in attr]
                if len(names) is len(set(names)):
                    raise ValidationError(elem + ' has duplicate names')
            elif require_all:
                raise ValidationError(
                    elem + ' must be defined for valid visualization')
dataset/ETHPy150Open wrobstory/vincent/vincent/visualization.py/Visualization.validate/operator `!=` -> `is`