input: Write a function to query the total population from the population_table.
  assert get_total_population() == 3196000000
  assert get_total_population() != 4000000000
output: def get_total_population():
      import sqlite3
      
      # Assuming the database connection and cursor are correctly set up
      conn = sqlite3.connect('example.db')
      cursor = conn.cursor()
      
      cursor.execute("SELECT SUM(population) FROM population_table")
      total_population = cursor.fetchone()[0]
      
      conn.close()
      return total_population