code: def mixed_float_frame():
      """
      Fixture for DataFrame of different float types with index of unique strings
  
      Columns are ['A', 'B', 'C', 'D'].
      """
      df = DataFrame(
          {
              col: np.random.default_rng(2).random(30, dtype=dtype)
              for col, dtype in zip(
                  list("ABCD"),
                  ["float32", "float32", "float32", "float64"],
              )
          },
          index=Index([f"foo_{i}" for i in range(30)], dtype=object),
      )
      # not supported by numpy random
      df["C"] = df["C"].astype("float16")
      return df
  
imports: import numpy
  import pytest
  from pandas import DataFrame, Index, NaT, date_range
label_desc: Use image node_id 3 for calling a global function with example usage: mixed_float_frame() and returns: df