[SPARK-3964] [MLlib] [PySpark] add Hypothesis test Python API

```
pyspark.mllib.stat.StatisticschiSqTest(observed, expected=None)
    :: Experimental ::

    If `observed` is Vector, conduct Pearson's chi-squared goodness
    of fit test of the observed data against the expected distribution,
    or againt the uniform distribution (by default), with each category
    having an expected frequency of `1 / len(observed)`.
    (Note: `observed` cannot contain negative values)

    If `observed` is matrix, conduct Pearson's independence test on the
    input contingency matrix, which cannot contain negative entries or
    columns or rows that sum up to 0.

    If `observed` is an RDD of LabeledPoint, conduct Pearson's independence
    test for every feature against the label across the input RDD.
    For each feature, the (feature, label) pairs are converted into a
    contingency matrix for which the chi-squared statistic is computed.
    All label and feature values must be categorical.

    :param observed: it could be a vector containing the observed categorical
                     counts/relative frequencies, or the contingency matrix
                     (containing either counts or relative frequencies),
                     or an RDD of LabeledPoint containing the labeled dataset
                     with categorical features. Real-valued features will be
                     treated as categorical for each distinct value.
    :param expected: Vector containing the expected categorical counts/relative
                     frequencies. `expected` is rescaled if the `expected` sum
                     differs from the `observed` sum.
    :return: ChiSquaredTest object containing the test statistic, degrees
             of freedom, p-value, the method used, and the null hypothesis.
```

Author: Davies Liu <davies@databricks.com>

Closes #3091 from davies/his and squashes the following commits:

145d16c [Davies Liu] address comments
0ab0764 [Davies Liu] fix float
5097d54 [Davies Liu] add Hypothesis test Python API

1 files changed, 6 insertions, 1 deletions

diff --git a/python/pyspark/mllib/common.py b/python/pyspark/mllib/common.py
index dbe5f698b7..c6149fe391 100644
--- a/python/pyspark/mllib/common.py
+++ b/python/pyspark/mllib/common.py
@@ -98,8 +98,13 @@ def _java2py(sc, r):
             jrdd = sc._jvm.SerDe.javaToPython(r)
             return RDD(jrdd, sc)
 
-        elif isinstance(r, (JavaArray, JavaList)) or clsName in _picklable_classes:
+        if clsName in _picklable_classes:
             r = sc._jvm.SerDe.dumps(r)
+        elif isinstance(r, (JavaArray, JavaList)):
+            try:
+                r = sc._jvm.SerDe.dumps(r)
+            except Py4JJavaError:
+                pass  # not pickable
 
     if isinstance(r, bytearray):
         r = PickleSerializer().loads(str(r))