code: def headers_to_sign(self, http_request):
          
          headers_to_sign = {}
          headers_to_sign = {'Host' : self.host}
          for name, value in http_request.headers.items():
              lname = name.lower()
              if lname.startswith('x-amz'):
                  headers_to_sign[name] = value
          return headers_to_sign
docs: Select the headers from the request that need to be included
          in the StringToSign.