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/plotting/plotgrid.py

@@ -0,0 +1,188 @@
+
+from sympy.external import import_module
+import sympy.plotting.backends.base_backend as base_backend
+
+
+# N.B.
+# When changing the minimum module version for matplotlib, please change
+# the same in the `SymPyDocTestFinder`` in `sympy/testing/runtests.py`
+
+
+__doctest_requires__ = {
+    ("PlotGrid",): ["matplotlib"],
+}
+
+
+class PlotGrid:
+    """This class helps to plot subplots from already created SymPy plots
+    in a single figure.
+
+    Examples
+    ========
+
+    .. plot::
+       :context: close-figs
+       :format: doctest
+       :include-source: True
+
+        >>> from sympy import symbols
+        >>> from sympy.plotting import plot, plot3d, PlotGrid
+        >>> x, y = symbols('x, y')
+        >>> p1 = plot(x, x**2, x**3, (x, -5, 5))
+        >>> p2 = plot((x**2, (x, -6, 6)), (x, (x, -5, 5)))
+        >>> p3 = plot(x**3, (x, -5, 5))
+        >>> p4 = plot3d(x*y, (x, -5, 5), (y, -5, 5))
+
+    Plotting vertically in a single line:
+
+    .. plot::
+       :context: close-figs
+       :format: doctest
+       :include-source: True
+
+        >>> PlotGrid(2, 1, p1, p2)
+        PlotGrid object containing:
+        Plot[0]:Plot object containing:
+        [0]: cartesian line: x for x over (-5.0, 5.0)
+        [1]: cartesian line: x**2 for x over (-5.0, 5.0)
+        [2]: cartesian line: x**3 for x over (-5.0, 5.0)
+        Plot[1]:Plot object containing:
+        [0]: cartesian line: x**2 for x over (-6.0, 6.0)
+        [1]: cartesian line: x for x over (-5.0, 5.0)
+
+    Plotting horizontally in a single line:
+
+    .. plot::
+       :context: close-figs
+       :format: doctest
+       :include-source: True
+
+        >>> PlotGrid(1, 3, p2, p3, p4)
+        PlotGrid object containing:
+        Plot[0]:Plot object containing:
+        [0]: cartesian line: x**2 for x over (-6.0, 6.0)
+        [1]: cartesian line: x for x over (-5.0, 5.0)
+        Plot[1]:Plot object containing:
+        [0]: cartesian line: x**3 for x over (-5.0, 5.0)
+        Plot[2]:Plot object containing:
+        [0]: cartesian surface: x*y for x over (-5.0, 5.0) and y over (-5.0, 5.0)
+
+    Plotting in a grid form:
+
+    .. plot::
+       :context: close-figs
+       :format: doctest
+       :include-source: True
+
+        >>> PlotGrid(2, 2, p1, p2, p3, p4)
+        PlotGrid object containing:
+        Plot[0]:Plot object containing:
+        [0]: cartesian line: x for x over (-5.0, 5.0)
+        [1]: cartesian line: x**2 for x over (-5.0, 5.0)
+        [2]: cartesian line: x**3 for x over (-5.0, 5.0)
+        Plot[1]:Plot object containing:
+        [0]: cartesian line: x**2 for x over (-6.0, 6.0)
+        [1]: cartesian line: x for x over (-5.0, 5.0)
+        Plot[2]:Plot object containing:
+        [0]: cartesian line: x**3 for x over (-5.0, 5.0)
+        Plot[3]:Plot object containing:
+        [0]: cartesian surface: x*y for x over (-5.0, 5.0) and y over (-5.0, 5.0)
+
+    """
+    def __init__(self, nrows, ncolumns, *args, show=True, size=None, **kwargs):
+        """
+        Parameters
+        ==========
+
+        nrows :
+            The number of rows that should be in the grid of the
+            required subplot.
+        ncolumns :
+            The number of columns that should be in the grid
+            of the required subplot.
+
+        nrows and ncolumns together define the required grid.
+
+        Arguments
+        =========
+
+        A list of predefined plot objects entered in a row-wise sequence
+        i.e. plot objects which are to be in the top row of the required
+        grid are written first, then the second row objects and so on
+
+        Keyword arguments
+        =================
+
+        show : Boolean
+            The default value is set to ``True``. Set show to ``False`` and
+            the function will not display the subplot. The returned instance
+            of the ``PlotGrid`` class can then be used to save or display the
+            plot by calling the ``save()`` and ``show()`` methods
+            respectively.
+        size : (float, float), optional
+            A tuple in the form (width, height) in inches to specify the size of
+            the overall figure. The default value is set to ``None``, meaning
+            the size will be set by the default backend.
+        """
+        self.matplotlib = import_module('matplotlib',
+            import_kwargs={'fromlist': ['pyplot', 'cm', 'collections']},
+            min_module_version='1.1.0', catch=(RuntimeError,))
+        self.nrows = nrows
+        self.ncolumns = ncolumns
+        self._series = []
+        self._fig = None
+        self.args = args
+        for arg in args:
+            self._series.append(arg._series)
+        self.size = size
+        if show and self.matplotlib:
+            self.show()
+
+    def _create_figure(self):
+        gs = self.matplotlib.gridspec.GridSpec(self.nrows, self.ncolumns)
+        mapping = {}
+        c = 0
+        for i in range(self.nrows):
+            for j in range(self.ncolumns):
+                if c < len(self.args):
+                    mapping[gs[i, j]] = self.args[c]
+                c += 1
+
+        kw = {} if not self.size else {"figsize": self.size}
+        self._fig = self.matplotlib.pyplot.figure(**kw)
+        for spec, p in mapping.items():
+            kw = ({"projection": "3d"} if (len(p._series) > 0 and
+                p._series[0].is_3D) else {})
+            cur_ax = self._fig.add_subplot(spec, **kw)
+            p._plotgrid_fig = self._fig
+            p._plotgrid_ax = cur_ax
+            p.process_series()
+
+    @property
+    def fig(self):
+        if not self._fig:
+            self._create_figure()
+        return self._fig
+
+    @property
+    def _backend(self):
+        return self
+
+    def close(self):
+        self.matplotlib.pyplot.close(self.fig)
+
+    def show(self):
+        if base_backend._show:
+            self.fig.tight_layout()
+            self.matplotlib.pyplot.show()
+        else:
+            self.close()
+
+    def save(self, path):
+        self.fig.savefig(path)
+
+    def __str__(self):
+        plot_strs = [('Plot[%d]:' % i) + str(plot)
+                      for i, plot in enumerate(self.args)]
+
+        return 'PlotGrid object containing:\n' + '\n'.join(plot_strs)