Compiles the signature for the specified executable and returns
        as a dictionary.

def _compile_signature(self, iexec, call_name):
        """Compiles the signature for the specified executable and returns
        as a dictionary."""
        if iexec is not None:
            summary = iexec.summary
            if isinstance(iexec, Function):
                summary = iexec.returns + "| " + iexec.summary
            elif isinstance(iexec, Subroutine) and len(iexec.modifiers) > 0:
                summary = ", ".join(iexec.modifiers) + " | " + iexec.summary
            elif isinstance(iexec, Interface):
                summary = iexec.describe()
            else:
                summary = iexec.summary

            #Add the name of the module who owns the method. Useful in case the
            #same executable is defined in multiple modules, but only one is
            #referenced in the current context.
            if iexec.parent is not None:
                summary += " | MODULE: {}".format(iexec.module.name)
            else:
                summary += " | BUILTIN"

            return dict(
                params=[p.name for p in iexec.ordered_parameters],
                index=0,
                call_name=call_name,
                description=summary,
            )        
        else:
            return []