functionToChangedParameters
val functionToChangedParameters: MutableMap<FunctionDeclaration, MutableMap<ValueDeclaration, MutableSet<Node>>>
Saves the information on which parameter(s) of a function are modified by the function. This is interesting since we need to add DFG edges between the modified parameter and the respective argument(s). For each ParameterDeclaration as well as the MethodDeclaration.receiver that has some incoming DFG-edge within this FunctionDeclaration, we store all previous DFG nodes.