ArcPy Python Toolbox - Update FieldMapping Parameters based on Feature Class Parameter Selector

Toolbox.pyt

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 = "Toolbox"
        self.alias = ""

        # List of tool classes associated with this toolbox
        self.tools = [Tool]


class Tool(object):
    def __init__(self):
        """Define the tool (tool name is the name of the class)."""
        self.label = "Tool"
        self.description = ""
        self.canRunInBackground = False

    def getParameterInfo(self):
        """Define parameter definitions"""
        feature_class_parameter = arcpy.Parameter(displayName="Input_Table", #0
                                        name="fc_settlements",
                                        datatype="DEFeatureClass",
                                        parameterType="Required",
                                        direction="Input")

        fieldMapParameter = arcpy.Parameter(displayName="Primary Settlement Fields", #1
                                name="primary_fieldmap",
                                datatype="GPFieldMapping",
                                parameterType="Optional",
                                enabled=True,
                                direction="Input" )
        fieldMapParameter.parameterDependencies = [feature_class_parameter.name] # Doesn't seem to work
        params = [feature_class_parameter,fieldMapParameter]
        return params

    def updateParameters(self, parameters):
        if parameters[0].altered:
           parameters[1].addTable(parameters[0].valueAsText) # Fails with method not found
        return

    def isLicensed(self):
        """Set whether tool is licensed to execute."""
        return True

    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

How do I change this so the two parameters are linked ? GIS SE Question : http://gis.stackexchange.com/questions/152659/how-to-update-field-mappings-parameter-on-table-selection-in-python-arctoolbox