Python: This example demonstrates how to collect common elements found in multiple lists.

Commonly Elements | .py

list1 = [1,2,3,4,5,6]
list2 = [3, 5, 7, 9]
results = list(set(list1).intersection(list2))
print results

Return list of items commonly found in multiple lists | .py

BLOCK_VALIDATION_DICT = {
    "Faction" : [ 
        "Note Properties" ,
        "ID Properties",
        "Wirecolor Properties"
    ],
    "FactionLink" : [
        "Object Properties",
        "Vray Properties",
        "Material Properties",
        "Atmospheric Properties",
        "Light Properties",
        "Note Properties",
        "Wirecolor Properties",
        "ID Properties"
    ],
    "Camera" : [ "Note Properties" ],
    "Pass" : [ 
        "Note Properties" ,
        "Wirecolor Properties"
    ],
}

blocks = ["Faction","Pass"]

def get_block_attributes(block_names=[]):
    valid_attributes = []
    if block_names:
        valid_attributes = BLOCK_VALIDATION_DICT.get( block_names[0] )
        
        for block_name in block_names[1:]: 
            attribute_names = BLOCK_VALIDATION_DICT.get(block_name)
            valid_attributes = list(set(valid_attributes).intersection(attribute_names))

    print valid_attributes
    return valid_attributes

get_block_attributes(block_names=blocks)