code: def validate_dataframe(df):
      if not isinstance(df, DataFrame):
          raise ValueError(
              "to_parquet only supports IO with DataFrames"
          )
  
      # must have value column names (strings only)
      if df.columns.inferred_type not in {"string", "unicode"}:
          raise ValueError("parquet must have string column names")
  
      # index level names must be strings
      valid_names = all(
          isinstance(name, string_types)
          for name in df.index.names
          if name is not None
      )
      if not valid_names:
          raise ValueError("Index level names must be strings")
  
imports: from distutils.version import LooseVersion
  from warnings import catch_warnings
  from pandas.compat import string_types
  from pandas.errors import AbstractMethodError
  from pandas import DataFrame, get_option
  from pandas.io.common import get_filepath_or_buffer, is_s3_url
label_desc: Use image node_id 1 for calling the BaseImpl obj's underlying member method code with example usage: obj.validate_dataframe(df) without return types