def gen_specs():
for fields_tuple in cls.imported_jar_library_spec_fields():
for item in target_representation.get(fields_tuple[field_pos],
()):
# For better error handling, this simply skips over non-strings, but we catch them
# with a WrongTargetType in JarLibrary.to_jar_dependencies.
if not isinstance(item, string_types):
raise JarLibrary.ExpectedAddressError(
'expected imports to contain string addresses, got {found_class} instead.'
.format(found_class=type(item).__name__))
yield item
