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/sets/contains.py

@@ -0,0 +1,63 @@
+from sympy.core import S
+from sympy.core.sympify import sympify
+from sympy.core.relational import Eq, Ne
+from sympy.core.parameters import global_parameters
+from sympy.logic.boolalg import Boolean
+from sympy.utilities.misc import func_name
+from .sets import Set
+
+
+class Contains(Boolean):
+    """
+    Asserts that x is an element of the set S.
+
+    Examples
+    ========
+
+    >>> from sympy import Symbol, Integer, S, Contains
+    >>> Contains(Integer(2), S.Integers)
+    True
+    >>> Contains(Integer(-2), S.Naturals)
+    False
+    >>> i = Symbol('i', integer=True)
+    >>> Contains(i, S.Naturals)
+    Contains(i, Naturals)
+
+    References
+    ==========
+
+    .. [1] https://en.wikipedia.org/wiki/Element_%28mathematics%29
+    """
+    def __new__(cls, x, s, evaluate=None):
+        x = sympify(x)
+        s = sympify(s)
+
+        if evaluate is None:
+            evaluate = global_parameters.evaluate
+
+        if not isinstance(s, Set):
+            raise TypeError('expecting Set, not %s' % func_name(s))
+
+        if evaluate:
+            # _contains can return symbolic booleans that would be returned by
+            # s.contains(x) but here for Contains(x, s) we only evaluate to
+            # true, false or return the unevaluated Contains.
+            result = s._contains(x)
+
+            if isinstance(result, Boolean):
+                if result in (S.true, S.false):
+                    return result
+            elif result is not None:
+                raise TypeError("_contains() should return Boolean or None")
+
+        return super().__new__(cls, x, s)
+
+    @property
+    def binary_symbols(self):
+        return set().union(*[i.binary_symbols
+            for i in self.args[1].args
+            if i.is_Boolean or i.is_Symbol or
+            isinstance(i, (Eq, Ne))])
+
+    def as_set(self):
+        return self.args[1]