test.py

import xml.etree.ElementTree as Et

tree = Et.ElementTree(file = 'test.xml')
root = tree.getroot()

for child in root:
  for grandchild in child:
    print(grandchild.findall('.//Raw_Material'))

test.xml

    <XML_Order order_Id='1' terms='Net30' ship_via='UPS'>
        <Line_Items>
            <Line_Item upc='1234567' item_id='1' color='blk' qty='15'>
                <Raw_Materials>
                    <Raw_Material Item_Id='H188' Vendor_Id='DI0001'/>
                    <Raw_Material Item_Id='ST03' Vendor_Id='DI0001'/>
                </Raw_Materials>
            </Line_Item>
            <Line_Item upc='12345678' item_id='1' color='blk' qty='15'>
                <Raw_Materials>
                    <Raw_Material Item_Id='H188' Vendor_Id='F10001'/>
                    <Raw_Material Item_Id='ST03' Vendor_Id='FI0001'/>
                </Raw_Materials>
            </Line_Item>
        </Line_Items>
    </XML_Order>