code: def test_only_one_dtype(test_data, df_from_dict):
      columns = list(test_data.keys())
      df = df_from_dict(test_data)
      dfX = df.__dataframe__()
  
      column_size = len(test_data[columns[0]])
      for column in columns:
          null_count = dfX.get_column_by_name(column).null_count
          assert null_count == 0
          assert isinstance(null_count, int)
          assert dfX.get_column_by_name(column).size() == column_size
          assert dfX.get_column_by_name(column).offset == 0
  
file_path: pandas/pandas/tests/interchange/test_spec_conformance.py
imports: import ctypes
  import math
  import pytest
  import pandas
label_desc: Use image node_id 2 for calling a global function with example usage: test_only_one_dtype(test_data, df_from_dict) without return types