code: def test_head_method(self, mock_read_sql):
      expected_data = pd.DataFrame(
          {"Column1": [1, 2, 3], "Column2": [4, 5, 6]}
      )
      mock_read_sql.return_value = expected_data
      head_data = self.connector.head()
      pd.testing.assert_frame_equal(head_data, expected_data)
  
imports: import unittest
  import pandas
  from unittest.mock import Mock, patch
  from pandasai.connectors.base import SQLConnectorConfig
  from pandasai.connectors.sql import PostgreSQLConnector, SQLConnector
  from pandasai.exceptions import MaliciousQueryError
label_desc: Use image node_id 5 for calling the TestSQLConnector obj's underlying member method code with example usage: obj.test_head_method(mock_read_sql) without return types