code: def _compare_fields(field1, field2, strict=True):
      
      if strict:
          # Return a simple equal test on the field minus the position.
          return field1[:4] == field2[:4]
      else:
          if field1[1:4] != field2[1:4]:
              # Different indicators or controlfield value.
              return False
          else:
              # Compare subfields in a loose way.
              return set(field1[0]) == set(field2[0])
docs: Compare 2 fields.
  
      If strict is True, then the order of the subfield will be taken care of, if
      not then the order of the subfields doesn't matter.
  
      :return: True if the field are equivalent, False otherwise.