<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _parse_package(cls, package_string):
 """ Helper method for parsing package string. Args: package_string (str):
 dash separated package string such as 'bash-4.2.39-3.el7' Returns: dict: dictionary containing 'name', 'version', 'release' and 'arch' keys """

        pkg, arch = rsplit(package_string, cls._arch_sep(package_string))
        if arch not in KNOWN_ARCHITECTURES:
            pkg, arch = (package_string, None)
        pkg, release = rsplit(pkg, '-')
        name, version = rsplit(pkg, '-')
        epoch, version = version.split(':', 1) if ":" in version else ['0', version]
        # oracleasm packages have a dash in their version string, fix that
        if name.startswith('oracleasm') and name.endswith('.el5'):
            name, version2 = name.split('-', 1)
            version = version2 + '-' + version
        return {
            'name': name,
            'version': version,
            'release': release,
            'arch': arch,
            'epoch': epoch
        }