def coerce(cls, key, value):
        """Convert list to MutationList."""
        if not isinstance(value, MutationList):
            if isinstance(value, list):
                return MutationList(value)

            # this call will raise ValueError
            return Mutable.coerce(key, value)
        else:
            return value
def coerce ( cls , key , value ) : if not isinstance ( value , MutationList ) : if isinstance ( value , list ) : return MutationList ( value ) return Mutable . coerce ( key , value ) else : return value
Convert list to MutationList.