def fromPy(cls, val, typeObj, vldMask=None):
        """
        :param val: None or dict {field name: field value}
        :param typeObj: instance of String HdlType
        :param vldMask: if is None validity is resolved from val
            if is 0 value is invalidated
            if is 1 value has to be valid
        """
        if vldMask == 0:
            val = None
        return cls(val, typeObj)
:param val: None or dict {field name: field value}
        :param typeObj: instance of String HdlType
        :param vldMask: if is None validity is resolved from val
            if is 0 value is invalidated
            if is 1 value has to be valid