def get_item_type(net, item_id):
    """Function to determine the item type for an item.
    
    Note: For meta-variables, which in shared-memory are stored
    besides items, this will return None.

    Parameter
    ---------
    net : dictionary
        The network dictionary.
    item_id : string
        The item name / identifier.
    
    Return
    ------
    item_type : str
        The type of the item (np, sp, plast or if).
    """
    item_type = None
    if item_id in net["neuron_pools"]:
        item_type = "np"
    elif item_id in net["synapse_pools"]:
        item_type = "sp"
    elif item_id in net["plasticities"]:
        item_type = "plast"
    elif item_id in net["interfaces"]:
        item_type = "if"
    return item_type