code: def test_unbalanced(self):
      # test that we can have a varying amount of time variables
      df = DataFrame(
          {
              "A2010": [1.0, 2.0],
              "A2011": [3.0, 4.0],
              "B2010": [5.0, 6.0],
              "X": ["X1", "X2"],
          }
      )
      df["id"] = df.index
      exp_data = {
          "X": ["X1", "X2", "X1", "X2"],
          "A": [1.0, 2.0, 3.0, 4.0],
          "B": [5.0, 6.0, np.nan, np.nan],
          "id": [0, 1, 0, 1],
          "year": [2010, 2010, 2011, 2011],
      }
      expected = DataFrame(exp_data)
      expected = expected.set_index(["id", "year"])[["X", "A", "B"]]
      result = wide_to_long(df, ["A", "B"], i="id", j="year")
      tm.assert_frame_equal(result, expected)
  
imports: import re
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, date_range, lreshape, melt, wide_to_long
  import pandas._testing
label_desc: Use image node_id 5 for calling the TestWideToLong obj's underlying member method code with example usage: obj.test_unbalanced() without return types