code: def test_ensure1d():
      out = ensure1d(1.0, "y")
      assert_equal(out, np.array([1.0]))
      out = ensure1d(np.arange(5.0), "y")
      assert_equal(out, np.arange(5.0))
      out = ensure1d(np.arange(5.0)[:, None], "y")
      assert_equal(out, np.arange(5.0))
      in_array = np.reshape(np.arange(16.0), (4, 4))
      with pytest.raises(ValueError):
          ensure1d(in_array, "y")
  
      y = Series(np.arange(5.0))
      ys = ensure1d(y, "y")
      assert isinstance(ys, np.ndarray)
      ys = ensure1d(y, "y", True)
      assert isinstance(ys, Series)
      y = DataFrame(y)
      ys = ensure1d(y, "y")
      assert isinstance(ys, np.ndarray)
      ys = ensure1d(y, "y", True)
      assert isinstance(ys, Series)
      y.columns = [1]
      ys = ensure1d(y, "y", True)
      assert isinstance(ys, Series)
      assert ys.name == "1"
      y = Series(np.arange(5.0), name="series")
      ys = ensure1d(y, "y")
      assert isinstance(ys, np.ndarray)
      ys = ensure1d(y, "y", True)
      assert isinstance(ys, Series)
      y = DataFrame(y)
      ys = ensure1d(y, "y")
      assert isinstance(ys, np.ndarray)
      ys = ensure1d(y, "y", True)
      assert isinstance(ys, Series)
      ys.name = 1
      ys = ensure1d(ys, None, True)
      assert isinstance(ys, Series)
      assert ys.name == "1"
      y = DataFrame(np.reshape(np.arange(10), (5, 2)))
      with pytest.raises(ValueError):
          ensure1d(y, "y")
  
imports: from abc import abstractmethod
  import datetime
  import numpy
  from numpy.random import RandomState
  from numpy.testing import assert_equal
  from pandas import DataFrame, Series, Timedelta, date_range
  import pytest
  from arch import doc
  from arch.univariate.base import implicit_constant
  from arch.utility.array import ConcreteClassMeta, DocStringInheritor, cutoff_to_index, date_to_index, ensure1d, ensure2d, find_index, parse_dataframe
label_desc: Use image node_id 2 for calling a global function with example usage: test_ensure1d() without return types