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/series/residues.py

@@ -0,0 +1,73 @@
+"""
+This module implements the Residue function and related tools for working
+with residues.
+"""
+
+from sympy.core.mul import Mul
+from sympy.core.singleton import S
+from sympy.core.sympify import sympify
+from sympy.utilities.timeutils import timethis
+
+
+@timethis('residue')
+def residue(expr, x, x0):
+    """
+    Finds the residue of ``expr`` at the point x=x0.
+
+    The residue is defined as the coefficient of ``1/(x-x0)`` in the power series
+    expansion about ``x=x0``.
+
+    Examples
+    ========
+
+    >>> from sympy import Symbol, residue, sin
+    >>> x = Symbol("x")
+    >>> residue(1/x, x, 0)
+    1
+    >>> residue(1/x**2, x, 0)
+    0
+    >>> residue(2/sin(x), x, 0)
+    2
+
+    This function is essential for the Residue Theorem [1].
+
+    References
+    ==========
+
+    .. [1] https://en.wikipedia.org/wiki/Residue_theorem
+    """
+    # The current implementation uses series expansion to
+    # calculate it. A more general implementation is explained in
+    # the section 5.6 of the Bronstein's book {M. Bronstein:
+    # Symbolic Integration I, Springer Verlag (2005)}. For purely
+    # rational functions, the algorithm is much easier. See
+    # sections 2.4, 2.5, and 2.7 (this section actually gives an
+    # algorithm for computing any Laurent series coefficient for
+    # a rational function). The theory in section 2.4 will help to
+    # understand why the resultant works in the general algorithm.
+    # For the definition of a resultant, see section 1.4 (and any
+    # previous sections for more review).
+
+    from sympy.series.order import Order
+    from sympy.simplify.radsimp import collect
+    expr = sympify(expr)
+    if x0 != 0:
+        expr = expr.subs(x, x + x0)
+    for n in (0, 1, 2, 4, 8, 16, 32):
+        s = expr.nseries(x, n=n)
+        if not s.has(Order) or s.getn() >= 0:
+            break
+    s = collect(s.removeO(), x)
+    if s.is_Add:
+        args = s.args
+    else:
+        args = [s]
+    res = S.Zero
+    for arg in args:
+        c, m = arg.as_coeff_mul(x)
+        m = Mul(*m)
+        if not (m in (S.One, x) or (m.is_Pow and m.exp.is_Integer)):
+            raise NotImplementedError('term of unexpected form: %s' % m)
+        if m == 1/x:
+            res += c
+    return res