code: def multi_substitution(*substitutions):
  	
  	substitutions = itertools.starmap(substitution, substitutions)
  	# compose function applies last function first, so reverse the
  	#  substitutions to get the expected order.
  	substitutions = reversed(tuple(substitutions))
  	return compose(*substitutions)
docs: Take a sequence of pairs specifying substitutions, and create
  	a function that performs those substitutions.
  
  	>>> multi_substitution(('foo', 'bar'), ('bar', 'baz'))('foo')
  	'baz'