Find items from an item collection that are in another item collection.

	Parameters:
		src (list): A list of item dicts or filepaths.
		dst (list): A list of item dicts or filepaths.
		fields (list): A list of fields used to compare item dicts.
		field_map (~collections.abc.Mapping): A mapping field name aliases.
			Default: :data:`~google_music_utils.constants.FIELD_MAP`
		normalize_values (bool): Normalize metadata values to remove common differences between sources.
			Default: ``False``
		normalize_func (function): Function to apply to metadata values if
			``normalize_values`` is ``True``.
			Default: :func:`~google_music_utils.utils.normalize_value`

	Yields:
		dict: The next item from ``src`` collection in ``dst`` collection.

def find_existing_items(
	src, dst, *, fields=None, field_map=None,
	normalize_values=False, normalize_func=normalize_value):
	"""Find items from an item collection that are in another item collection.

	Parameters:
		src (list): A list of item dicts or filepaths.
		dst (list): A list of item dicts or filepaths.
		fields (list): A list of fields used to compare item dicts.
		field_map (~collections.abc.Mapping): A mapping field name aliases.
			Default: :data:`~google_music_utils.constants.FIELD_MAP`
		normalize_values (bool): Normalize metadata values to remove common differences between sources.
			Default: ``False``
		normalize_func (function): Function to apply to metadata values if
			``normalize_values`` is ``True``.
			Default: :func:`~google_music_utils.utils.normalize_value`

	Yields:
		dict: The next item from ``src`` collection in ``dst`` collection.
	"""

	if field_map is None:
		field_map = FIELD_MAP

	dst_keys = {
		_gather_field_values(
			dst_item, fields=fields, field_map=field_map,
			normalize_values=normalize_values, normalize_func=normalize_func
		) for dst_item in dst
	}

	for src_item in src:
		if _gather_field_values(
			src_item, fields=fields, field_map=field_map,
			normalize_values=normalize_values, normalize_func=normalize_func
		) in dst_keys:
			yield src_item