'The version up to the specified component.
Examples:
>>> version = Version(\'1.23-4b\')
>>> version.up_to(1)
Version(\'1\')
>>> version.up_to(2)
Version(\'1.23\')
>>> version.up_to(3)
Version(\'1.23-4\')
>>> version.up_to(4)
Version(\'1.23-4b\')
>>> version.up_to(-1)
Version(\'1.23-4\')
>>> version.up_to(-2)
Version(\'1.23\')
>>> version.up_to(-3)
Version(\'1\')
Returns:
Version: The first index components of the version'

def up_to(self, index):

    return self[:index]
