Represents a resource to download, extract, or both.
__init__( url=None, extract_method=None, path=None )
str, the URL at which to download the resource.
ExtractMethodto be used to extract resource. If not set, will be guessed from downloaded file name
str, path of resource on local disk. Can be None if resource has not be downloaded yet. In such case,
urlmust be set.
ExtractMethod to use on resource. Cannot be None.
@classmethod exists_locally( cls, path )
Returns whether the resource exists locally, at