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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _complete_sig(self, symbol, attribute):
 """Suggests completion for calling a function or subroutine."""

        #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)