code: def _complete_sig(self, symbol, attribute):
          
          #Return a list of valid parameters for the function being called
          fncall = self.context.el_name
          iexec, execmod = self.context.parser.tree_find(fncall, self.context.module, "executables")
  
          if iexec is None:
              #Try the interfaces as a possible executable to complete.
              iexec, execmod = self.context.parser.tree_find(fncall, self.context.module, "interfaces")
  
          if iexec is not None:
              if symbol == "":
                  return iexec.parameters
              else:
                  result = {}
                  for ikey in iexec.parameters:
                      if self._symbol_in(symbol, ikey):
                          result[ikey] = iexec.parameters[ikey]
                  return result
          else:
              return self._complete_word(symbol, attribute)
docs: Suggests completion for calling a function or subroutine.