code: def _check_cast(df, v):
      """
      Check if all dtypes of df are equal to v
      """
      assert all(s.dtype.name == v for _, s in df.items())
  
imports: import re
  import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import Categorical, CategoricalDtype, DataFrame, DatetimeTZDtype, Index, Interval, IntervalDtype, NaT, Series, Timedelta, Timestamp, concat, date_range, option_context
  import pandas._testing
label_desc: Use image node_id 1 for calling a global function with example usage: _check_cast(df, v) without return types