Find a given category/namespace/name combination in the registry
    category - string, see utils.inputs.registrycategories
    namespace - module namespace, see settings.NAMESPACE
    name - lowercase name of module

def find_in_registry(category = None, namespace = None, name = None):
    """
    Find a given category/namespace/name combination in the registry
    category - string, see utils.inputs.registrycategories
    namespace - module namespace, see settings.NAMESPACE
    name - lowercase name of module
    """
    selected_registry = registry
    if category is not None:
        selected_registry = [re for re in selected_registry if re.category==category]
    if namespace is not None:
        selected_registry = [re for re in selected_registry if re.namespace==namespace]
    if name is not None:
        selected_registry = [re for re in selected_registry if re.name==name]
    if len(selected_registry)>0:
        return [sr.cls for sr in selected_registry]

    return None