Get schema type for the argument

        :param schema: Schema to analyze
        :return: COMPILED_TYPE constant
        :rtype: str|None

def get_schema_type(cls, schema):
        """ Get schema type for the argument

        :param schema: Schema to analyze
        :return: COMPILED_TYPE constant
        :rtype: str|None
        """
        schema_type = type(schema)

        # Marker
        if issubclass(schema_type, markers.Marker):
            return const.COMPILED_TYPE.MARKER
        # Marker Type
        elif issubclass(schema_type, six.class_types) and issubclass(schema, markers.Marker):
            return const.COMPILED_TYPE.MARKER
        # CompiledSchema
        elif isinstance(schema, CompiledSchema):
            return const.COMPILED_TYPE.SCHEMA
        else:
            return primitive_type(schema)