@classmethod
def from_curve_map(cls, dt_valuation, curve_map):
    """Create market consisting of a map of curves.

        The map is a dictionary of dictionaries.
        The top level keys are currency strings.
        The next level are strings describing the curves in that currency.
        One curve key in each currency must be named 'discount'.
        The others are frequencies defined as an integer number of months.

        These 'frequency' curves are used to produce forward ibor rates,
        from pseudo-discount factors.
        """
    return cls(dt_valuation, curve_map)
