code: def test_sum(self):
      pdf = pd.DataFrame(
          {"a": [1, 2, 3, np.nan], "b": [0.1, np.nan, 0.3, np.nan]}
      )
      psdf = ps.from_pandas(pdf)
  
      self.assert_eq(psdf.sum(), pdf.sum())
      self.assert_eq(psdf.sum(axis=1), pdf.sum(axis=1))
      self.assert_eq(psdf.sum(min_count=3), pdf.sum(min_count=3))
      self.assert_eq(
          psdf.sum(axis=1, min_count=1), pdf.sum(axis=1, min_count=1)
      )
      self.assert_eq(psdf.loc[[]].sum(), pdf.loc[[]].sum())
      self.assert_eq(
          psdf.loc[[]].sum(min_count=1), pdf.loc[[]].sum(min_count=1)
      )
  
      self.assert_eq(psdf["a"].sum(), pdf["a"].sum())
      self.assert_eq(
          psdf["a"].sum(min_count=3), pdf["a"].sum(min_count=3)
      )
      self.assert_eq(
          psdf["b"].sum(min_count=3), pdf["b"].sum(min_count=3)
      )
      self.assert_eq(psdf["a"].loc[[]].sum(), pdf["a"].loc[[]].sum())
      self.assert_eq(
          psdf["a"].loc[[]].sum(min_count=1),
          pdf["a"].loc[[]].sum(min_count=1),
      )
  
imports: import numpy
  import pandas
  from pyspark import pandas
  from pyspark.testing.pandasutils import PandasOnSparkTestCase, SPARK_CONF_ARROW_ENABLED
  from pyspark.testing.sqlutils import SQLTestUtils
label_desc: Use image node_id 5 for calling the StatsTestsMixin obj's underlying member method code with example usage: obj.test_sum() without return types