%External.GeneralImpl is an abstract class that implements the %External.Interface interface
and defines and provides the implementation for %SYSTEM.external class interface.
This class is not to be used directly. Internal use only. For the public interface, refer to
Internal Note: The interface for GeneralImpl is the same as for System with one notable exception - all methods accept an
External Language Server name. Be sure to keep the API consistent between them.
Return a new gateway connection to an External Language Server. This method does not
retrieve an existing cached gateway connection. It always acquires a new gateway connection
to the requested External Language Server.
Invoke external code. If invoke() is called as an expression then return any value returned by the external code.
If no value is returned by the external code then a <COMMAND> exception is thrown. The externalClass is expected to be
passed as the name of the external code container. For Java this is the Java class name. For Python this can be the
name of a class or module. The externalMethod is the name of the external unit of code (function, method, etc.) to invoke in
the externalClass container. The return value is the value returned by the external code.
If the external method does not return a value then invoke() does not return a value.