import re


def get_simple_version(version_string):
    """Extract the version number without the ><= requirements.

    This simply extracts the version number without the ><= requirement so
    it will not be accurate for version requirements that are not >=, <= or
    = to a version.

    >>> get_simple_version('>=33.0a1')
    '33.0a1'
    """
    if not version_string:
        return ''
    return re.sub('[<=>]', '', version_string)