code: def content_type(self, value=None):
  		
  		content_type = self.normalize_name('Content-Type')
  		if value is not None:
  			self.replace_headers(content_type, value)
  		if content_type in self.__headers.keys():
  			return self.__headers[content_type][0]
docs: Set (replace) and or get "Content-Type" header value
  
  		:param value: value to set (if specified)
  		:return: None if header doesn't exist, otherwise - str