'Generates request headers given a storage class name.
:keyword storage_class: The name of the S3 object\'s storage class
:type extra: ``str``
:return: Headers to include in a request
:rtype: :dict:'

def _to_storage_class_headers(self, storage_class):

    headers = {}
    storage_class = (storage_class or 'standard')
    if (storage_class not in ['standard', 'reduced_redundancy']):
        raise ValueError(('Invalid    storage    class    value:    %s' % storage_class))
    key = (self.http_vendor_prefix + '-storage-class')
    headers[key] = storage_class.upper()
    return headers
