input: from typing import List
  
  
  def insert_delimiter(numbers: List[int], delimiter: int) -> List[int]:
      """ Place a specified number 'delimiter' between each pair of adjacent items in the input list `numbers`
      >>> insert_delimiter([], 4)
      []
      >>> insert_delimiter([1, 2, 3], 4)
      [1, 4, 2, 4, 3]
      """
output:     if not numbers:
          return []
      result = []
      for i in range(len(numbers) - 1):
          result.append(numbers[i])
          result.append(delimiter)
      result.append(numbers[-1])
      return result