code: def get_headers(self, instant):
          
          headers = {'x-amz-date': _auth_v4.makeAMZDate(instant)}
          if self.body_producer is None:
              data = self.data
              if data is None:
                  data = b""
              headers["x-amz-content-sha256"] = hashlib.sha256(data).hexdigest()
          else:
              data = None
              headers["x-amz-content-sha256"] = b"UNSIGNED-PAYLOAD"
          for key, value in self.metadata.iteritems():
              headers["x-amz-meta-" + key] = value
          for key, value in self.amz_headers.iteritems():
              headers["x-amz-" + key] = value
  
          # Before we check if the content type is set, let's see if we can set
          # it by guessing the the mimetype.
          self.set_content_type()
          if self.content_type is not None:
              headers["Content-Type"] = self.content_type
          if self.creds is not None:
              headers["Authorization"] = self.sign(
                  headers,
                  data,
                  s3_url_context(self.endpoint, self.bucket, self.object_name),
                  instant,
                  method=self.action)
          return headers
docs: Build the list of headers needed in order to perform S3 operations.