Retrieve the electrical bill of materials for a specific PCB version.

The bom key points to an object whose parts array has one entry for each component
(designator) on the board. While several of the part keys are obvious in their meaning, some
require more detail:

populate

The populate key indicates whether you have specified that the particular instance of that
component be populated on the board. By default, it is set to true, unless you have marked the
component "Do not place" in the Bill of Materials view for the PCB in the user interface. This
key having a value of true does not, however, ensure the part's population in assembly. The
component must also have a part to source.

approved_vendor_list

Every BOM line is sourced through an approved vendor list (AVL): the manufacturer parts that
may be used for that line, in order of preference. A single MPN can be manufactured by a number
of vendors, so every manufacturer part has a unique part_id. Lines that use the same part
share the same approved_vendor_list_id, so use it to group lines. Manage AVLs with the Approved
Vendor List endpoints.

sourcing_default

How the line is sourced: macrofab (MacroFab purchases a part from the AVL) or customer (you
supply one). Change it with PUT /api/v3/pcb/{pcb_id}/{pcb_version}/sourcing/defaults. The
older origin field is deprecated and not used.

selected_part, selected_mpn

These fields are deprecated and are generally null. Parts are not selected on the BOM: when
a PCB is quoted, MacroFab chooses the part for each line from its approved vendor list, based
on the list's priority (precedence_preference and list_precedence) and the market
availability of the parts on it.