code: def has_dtypes(df, items):
      
      dtypes = df.dtypes
      for k, v in items.items():
          if not dtypes[k] == v:
              raise AssertionError("{} has the wrong dtype. Should be ({}), is ({})".format(k, v,dtypes[k]))
      return df
docs: Assert that a DataFrame has ``dtypes``
  
      Parameters
      ==========
      df: DataFrame
      items: dict
        mapping of columns to dtype.
  
      Returns
      =======
      df : DataFrame