stdlib: Add SparseHist to PyStats

This is inclusive of tests to ensure they have implemented correctly.

Change-Id: I5c84d5ffdb7b914936cfd86ca012a7b141eeaf42

src/python/pybind11/stats.cc

@@ -78,6 +78,7 @@ cast_stat_info(const statistics::Info *info)
     TRY_CAST(statistics::VectorInfo);
     TRY_CAST(statistics::Vector2dInfo);
     TRY_CAST(statistics::DistInfo);
+    TRY_CAST(statistics::SparseHistInfo);
 
     return py::cast(info);
 
@@ -195,6 +196,15 @@ pybind_init_stats(py::module_ &m_native)
         .def_readonly("value", &statistics::Vector2dInfo::cvec)
         ;
 
+    py::class_<statistics::SparseHistInfo, statistics::Info,
+               std::unique_ptr<statistics::SparseHistInfo, py::nodelete>>(
+                    m, "SparseHistInfo")
+        .def_property_readonly("values", //A Dict[float, int] of sample & count
+            [](const statistics::SparseHistInfo &info) {
+                return info.data.cmap;
+            })
+        ;
+
     py::class_<statistics::FormulaInfo, statistics::VectorInfo,
                std::unique_ptr<statistics::FormulaInfo, py::nodelete>>(
                       m, "FormulaInfo")