in fluent/migrate/transforms.py [0:0]
def chain_elements(elements):
"""Flatten a list of FTL nodes into an iterator over PatternElements."""
for element in elements:
if isinstance(element, FTL.Pattern):
# PY3 yield from element.elements
yield from element.elements
elif isinstance(element, FTL.PatternElement):
yield element
elif isinstance(element, FTL.Expression):
yield FTL.Placeable(element)
else:
raise RuntimeError("Expected Pattern, PatternElement or Expression")