chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/sympy/interactive/traversal.py

@@ -0,0 +1,95 @@
+from sympy.core.basic import Basic
+from sympy.printing import pprint
+
+import random
+
+def interactive_traversal(expr):
+    """Traverse a tree asking a user which branch to choose. """
+
+    RED, BRED = '\033[0;31m', '\033[1;31m'
+    GREEN, BGREEN = '\033[0;32m', '\033[1;32m'
+    YELLOW, BYELLOW = '\033[0;33m', '\033[1;33m'  # noqa
+    BLUE, BBLUE = '\033[0;34m', '\033[1;34m'      # noqa
+    MAGENTA, BMAGENTA = '\033[0;35m', '\033[1;35m'# noqa
+    CYAN, BCYAN = '\033[0;36m', '\033[1;36m'      # noqa
+    END = '\033[0m'
+
+    def cprint(*args):
+        print("".join(map(str, args)) + END)
+
+    def _interactive_traversal(expr, stage):
+        if stage > 0:
+            print()
+
+        cprint("Current expression (stage ", BYELLOW, stage, END, "):")
+        print(BCYAN)
+        pprint(expr)
+        print(END)
+
+        if isinstance(expr, Basic):
+            if expr.is_Add:
+                args = expr.as_ordered_terms()
+            elif expr.is_Mul:
+                args = expr.as_ordered_factors()
+            else:
+                args = expr.args
+        elif hasattr(expr, "__iter__"):
+            args = list(expr)
+        else:
+            return expr
+
+        n_args = len(args)
+
+        if not n_args:
+            return expr
+
+        for i, arg in enumerate(args):
+            cprint(GREEN, "[", BGREEN, i, GREEN, "] ", BLUE, type(arg), END)
+            pprint(arg)
+            print()
+
+        if n_args == 1:
+            choices = '0'
+        else:
+            choices = '0-%d' % (n_args - 1)
+
+        try:
+            choice = input("Your choice [%s,f,l,r,d,?]: " % choices)
+        except EOFError:
+            result = expr
+            print()
+        else:
+            if choice == '?':
+                cprint(RED, "%s - select subexpression with the given index" %
+                       choices)
+                cprint(RED, "f - select the first subexpression")
+                cprint(RED, "l - select the last subexpression")
+                cprint(RED, "r - select a random subexpression")
+                cprint(RED, "d - done\n")
+
+                result = _interactive_traversal(expr, stage)
+            elif choice in ('d', ''):
+                result = expr
+            elif choice == 'f':
+                result = _interactive_traversal(args[0], stage + 1)
+            elif choice == 'l':
+                result = _interactive_traversal(args[-1], stage + 1)
+            elif choice == 'r':
+                result = _interactive_traversal(random.choice(args), stage + 1)
+            else:
+                try:
+                    choice = int(choice)
+                except ValueError:
+                    cprint(BRED,
+                           "Choice must be a number in %s range\n" % choices)
+                    result = _interactive_traversal(expr, stage)
+                else:
+                    if choice < 0 or choice >= n_args:
+                        cprint(BRED, "Choice must be in %s range\n" % choices)
+                        result = _interactive_traversal(expr, stage)
+                    else:
+                        result = _interactive_traversal(args[choice], stage + 1)
+
+        return result
+
+    return _interactive_traversal(expr, 0)