Get inner evaluation count and names.

def __get_eval_info(self):
        """Get inner evaluation count and names."""
        if self.__need_reload_eval_info:
            self.__need_reload_eval_info = False
            out_num_eval = ctypes.c_int(0)
            # Get num of inner evals
            _safe_call(_LIB.LGBM_BoosterGetEvalCounts(
                self.handle,
                ctypes.byref(out_num_eval)))
            self.__num_inner_eval = out_num_eval.value
            if self.__num_inner_eval > 0:
                # Get name of evals
                tmp_out_len = ctypes.c_int(0)
                string_buffers = [ctypes.create_string_buffer(255) for i in range_(self.__num_inner_eval)]
                ptr_string_buffers = (ctypes.c_char_p * self.__num_inner_eval)(*map(ctypes.addressof, string_buffers))
                _safe_call(_LIB.LGBM_BoosterGetEvalNames(
                    self.handle,
                    ctypes.byref(tmp_out_len),
                    ptr_string_buffers))
                if self.__num_inner_eval != tmp_out_len.value:
                    raise ValueError("Length of eval names doesn't equal with num_evals")
                self.__name_inner_eval = \
                    [string_buffers[i].value.decode() for i in range_(self.__num_inner_eval)]
                self.__higher_better_inner_eval = \
                    [name.startswith(('auc', 'ndcg@', 'map@')) for name in self.__name_inner_eval]