arcgis10.2.2的python工具箱中值表类型（GPValueTable）的参数如何对其某一列（column）设置过滤器（filter）

import arcpy



class Toolbox(object):

    def __init__(self):

        """Define the toolbox (the name of the toolbox is the name of the

        .pyt file)."""

        self.label = "test"

        self.alias = "test"



        # List of tool classes associated with this toolbox

        self.tools = [testTool1]



class testTool1(object):

    def __init__(self):

        """Define the tool (tool name is the name of the class)."""

        self.label = "testTool"

        self.description = "test"

        self.canRunInBackground = False



    def getParameterInfo(self):

        in_fc = arcpy.Parameter(

            name='in_features',

            displayName='Input Features',

            datatype='GPFeatureLayer',

            direction='Input',

            parameterType='Required')

        vt = arcpy.Parameter(

            name='summary_fields',

            displayName='Image Time(optial)',

            datatype='GPValueTable',

            direction='Input',

            parameterType='Optional')

        vt.parameterDependencies = [in_fc.name]

        vt.columns = [['GPString', 'Image Time'], ['GPString', 'Image Mosaic'], ['GPString', 'Image Layer']]

        vt.filters[0].type = 'ValueList'

        vt.filters[0].list = ["2019","2020"]

        vt.filters[1].type = 'ValueList'

        vt.filters[1].list = ["xqx2019","xqx2020"]

        vt.filters[2].type = 'ValueList'

        vt.filters[2].list = ["tc2019","tc2020"]

        vt.values = [['2019', 'xqx2019','tc2019']]



        params=[in_fc,vt]



        return params



    def isLicensed(self):

        """Set whether tool is licensed to execute."""

        return True



    def updateParameters(self, parameters):

        

        return



    def updateMessages(self, parameters):

        """Modify the messages created by internal validation for each tool

        parameter.  This method is called after internal validation."""

        return



    def execute(self, parameters, messages):

        """The source code of the tool."""



        return