Python3 Huffman Implementation help, write code underneath functions

class HuffmanNode:
	def __init__(self, char, freq):
	self.char = char # stored as an integer - the ASCII character code value
	self.freq = freq # the freqency associated with the node
	self.left = None # Huffman tree (node) to the left
	self.right = None # Huffman tree (node) to the right
	def set_left(self, node):
	self.left = node
	def set_right(self, node):
	self.right = node
	def comes_before(a, b):
	"""Returns True if tree rooted at node a comes before tree rooted at node b, False otherwise"""
	def combine(a, b):
	"""Creates and returns a new Huffman node with children a and b, with the "lesser node" on the left
	The new node's frequency value will be the sum of the a and b frequencies
	The new node's char value will be the lesser of the a and b char ASCII values"""
	def cnt_freq(filename):
	"""Opens a text file with a given file name (passed as a string) and counts the
	frequency of occurrences of all the characters within that file"""
	def create_huff_tree(char_freq):
	"""Create a Huffman tree for characters with non-zero frequency
	Returns the root node of the Huffman tree"""
	def create_code(node):
	"""Returns an array (Python list) of Huffman codes. For each character, use the integer ASCII representation
	as the index into the arrary, with the resulting Huffman code for that character stored at that location"""
	def create_header(freqs):
	"""Input is the list of frequencies. Creates and returns a header for the output file
	Example: For the frequency list asscoaied with "aaabbbbcc, would return 97 3 98 4 99 2 """
	def huffman_encode(in_file, out_file):
	"""Takes inout file name and output file name as parameters
	Uses the Huffman coding process on the text from the input file and writes encoded text to output file
	Take not of special cases - empty file and file with only one unique character"""