def get_dimension_type(self, dim):
        """Get the type of the requested dimension.

        Type is determined by Dimension.type attribute or common
        type of the dimension values, otherwise None.

        Args:
            dimension: Dimension to look up by name or by index

        Returns:
            Declared type of values along the dimension
        """
        dim = self.get_dimension(dim)
        if dim is None:
            return None
        elif dim.type is not None:
            return dim.type
        elif dim in self.vdims:
            return np.float64
        return self.interface.dimension_type(self, dim)
Get the type of the requested dimension.

        Type is determined by Dimension.type attribute or common
        type of the dimension values, otherwise None.

        Args:
            dimension: Dimension to look up by name or by index

        Returns:
            Declared type of values along the dimension