input: 
  def find_minimum_integer(data_structure: IntList) -> int:
      """
      Find and return the minimum integer value stored in the given data structure.
      
      >>> int_list = IntList()
      >>> int_list.add_value(5)
      >>> int_list.add_value(3)
      >>> int_list.add_value(7)
      >>> find_minimum_integer(int_list)
      3
      >>> int_list.add_value(1)
      >>> find_minimum_integer(int_list)
      1
      """
  
output:     min_value = float('inf')
      for value in data_structure.get_values():
          if value < min_value:
              min_value = value
      return min_value