code: def test_fillna_dict(using_copy_on_write):
      df = DataFrame({"a": [1.5, np.nan], "b": 1})
      df_orig = df.copy()
  
      df2 = df.fillna({"a": 100.5})
      if using_copy_on_write:
          assert np.shares_memory(
              get_array(df, "b"), get_array(df2, "b")
          )
          assert not np.shares_memory(
              get_array(df, "a"), get_array(df2, "a")
          )
      else:
          assert not np.shares_memory(
              get_array(df, "b"), get_array(df2, "b")
          )
  
      df2.iloc[0, 1] = 100
      tm.assert_frame_equal(df_orig, df)
  
imports: import numpy
  import pytest
  from pandas import NA, ArrowDtype, DataFrame, Interval, NaT, Series, Timestamp, interval_range, option_context
  import pandas._testing
  from pandas.tests.copy_view.util import get_array
label_desc: Use image node_id 13 for calling a global function with example usage: test_fillna_dict(using_copy_on_write) without return types