Validate a colormap

    Parameters
    ----------
    val: str or :class:`mpl.colors.Colormap`

    Returns
    -------
    str or :class:`mpl.colors.Colormap`

    Raises
    ------
    ValueError

def validate_cmap(val):
    """Validate a colormap

    Parameters
    ----------
    val: str or :class:`mpl.colors.Colormap`

    Returns
    -------
    str or :class:`mpl.colors.Colormap`

    Raises
    ------
    ValueError"""
    from matplotlib.colors import Colormap
    try:
        return validate_str(val)
    except ValueError:
        if not isinstance(val, Colormap):
            raise ValueError(
                "Could not find a valid colormap!")
        return val