<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def render_pep440(vcs):
 """Convert git release tag into a form that is PEP440 compliant."""


    if vcs is None:
        return None

    tags = vcs.split('-')

    # Bare version number
    if len(tags) == 1:
        return tags[0]
    else:
        return tags[0] + '+' + '.'.join(tags[1:])