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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_group(group_or_groupname):
 """Return Plone Group :param group_or_groupname: Plone group or the name of the group :type groupname: GroupData/str :returns: Plone GroupData """

    if not group_or_groupname:

        return None
    if hasattr(group_or_groupname, "_getGroup"):
        return group_or_groupname
    gtool = get_tool("portal_groups")
    return gtool.getGroupById(group_or_groupname)