@staticmethod
def _check_activity(activity, _length, _type):
    """
        Verifies that the activity is valid.

        Args:
            activity (iterable): Array of activity
            _length (int): Count of all points
            _type (string): 'points' or 'triangles'
        """
    if len(activity) != _length:
        raise ValueError(
            'Length of activity must be equal to the length of {}.'.format(
            _type))
