[NTG-context] How do I handle strings with " characters in it in METAPOST?

I am using MetaFun (Lua code) to create METAPOST commands from an XML file. One of the issues I am running into that in METAPOST I have to handle strings with " characters in them and METAPOST doesn’t like those. The argument using the string Foo "Bar” Foo turns into someCall( "Foo “Bar” Foo”) I guess I have to change the string into something with explicit character codes for the " characters, maybe? In a later stage, these strings will be typeset by the ConTeXt side of things so they fit into a certain area within the METAPOST picture. What is my best approach? G