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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_schema(self, argmap, req):
 """Return a `marshmallow.Schema` for the given argmap and request. :param argmap: Either a `marshmallow.Schema`, `dict` of argname -> `marshmallow.fields.Field` pairs, or a callable that returns a `marshmallow.Schema` instance. :param req: The request object being parsed. :rtype: marshmallow.Schema """

        if isinstance(argmap, ma.Schema):
            schema = argmap
        elif isinstance(argmap, type) and issubclass(argmap, ma.Schema):
            schema = argmap()
        elif callable(argmap):
            schema = argmap(req)
        else:
            schema = dict2schema(argmap, self.schema_class)()
        if MARSHMALLOW_VERSION_INFO[0] < 3 and not schema.strict:
            warnings.warn(
                "It is highly recommended that you set strict=True on your schema "
                "so that the parser's error handler will be invoked when expected.",
                UserWarning,
            )
        return schema