'Attempt to uninstall requirements. Returns 0 if successfull, else None.'

def uninstall_dependencies(self, index=None, **payload):

    requirements = payload.get('requirements')
    if (not requirements):
        return None
    if index:
        resolver = self._dependency_resolvers[index]
        if resolver.can_uninstall_dependencies:
            return resolver.uninstall(requirements)
    else:
        for index in self.uninstallable_resolvers:
            return_code = self._dependency_resolvers[index].uninstall(requirements)
            if (return_code == 0):
                return return_code
    return None
