code: def append_code(original, codefile):
      
      with open(codefile) as code, open(original, "a") as o:
          o.write("\n")
          o.writelines(code)
docs: Append the contents of one file to another.
  
      :param original: name of file that will be appended to
      :type original: str
      :param codefile: name of file that will be appende
      :type codefile: str
  
      This function is particularly useful when one wants to replace a function
      in student code with their own implementation of one. If two functions are
      defined with the same name in Python, the latter definition is taken so overwriting
      a function is as simple as writing it to a file and then appending it to the
      student's code.
  
      Example usage::
  
          # Include a file containing our own implementation of a lookup function.
          check50.include("lookup.py")
  
          # Overwrite the lookup function in helpers.py with our own implementation.
          check50.py.append_code("helpers.py", "lookup.py")