Git Source Structure used to represent a foreign call that can be made during rule evaluation 
struct ForeignCall {
    bool set;
    address foreignCallAddress;
    bytes4 signature;
    ParamTypes returnType;
    uint256 foreignCallIndex;
    ParamTypes[] parameterTypes;
    ForeignCallEncodedIndex[] encodedIndices;
    ForeignCallEncodedIndex[] mappedTrackerKeyIndices;
    bytes4 callingFunctionSelector;
}