Merge branch 'change_doc_tree' of https://github.com/PaddlePaddle/FluidDoc into change_doc_tree

doc/paddle/api/gen_alias_mapping.sh

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#!/usr/bin/env bash
+
+if [[ $# -ne 1 ]]; then
+    echo -e "Usage:\n\t./gen_alias_mapping.sh <PADDLE_ROOT_DIR>"
+    exit 1
+else
+    PADDLE_ROOT=$1
+fi
+
+find ${PADDLE_ROOT}/python/ -name '*.py' \
+    | xargs  grep -v '^#' \
+    | grep 'DEFINE_ALIAS' \
+    | perl -ne '
+        if (/^.*\/python\/(.*):from (\.*)(\w.*) import (.*?)\s+#DEFINE_ALIAS\s+$/) {
+            my @arr = split(", ", $4); 
+            foreach $i (@arr) {
+                printf "%s|%s|%s|%d\n", $3, $i, substr($1, 0, -3), length($2);
+            }
+        }' \
+    | awk -F '[|/]' '
+        {
+            key = "";
+            val = "";
+            if ($2 ~ /.* as .*/) {
+                split($2, arr, " as ");
+                old = arr[1];
+                new = arr[2];
+            } else {
+                old = $2;
+                new = $2;
+            }
+            for (i = 3; i <= (NF - 1 - $NF); ++i) {
+                val = val""$i".";
+            }
+            val =  val""$1"."old
+            for (i = 3; i <= (NF - 1); ++i) {
+                if ($i != "__init__") {
+                    key = key""$i".";
+                }
+            }
+            key = key""new;
+            n2o[key] = val;
+        } 
+        END {
+            for (new in n2o) {
+                old = n2o[new] in n2o ? n2o[n2o[new]] : n2o[new];
+                print old, length(new), new;
+            }
+        }' \
+    | sort -k 1,1 -k 2n,2 \
+    | awk '
+        {
+            o2n[$1] = o2n[$1] ? o2n[$1]","$3 : $3;
+        }
+        END { 
+            for (i in o2n) {
+                print i"\t"o2n[i];
+            }
+        }'
+