@classmethod<EOL><INDENT>def bend(cls, mapping, context=None):<DEDENT>
return ForallBend(mapping, context)<EOL>
Return a ForallBend instance that bends each element of the list with the
given mapping.

mapping: a JSONBender mapping as passed to the `bend()` function.
context: optional. the context that will be passed to `bend()`.
         Note that if context is not passed, it defaults at bend-time
         to the one passed to the outer mapping.

Example:
```
source = [{'a': 23}, {'a': 27}]
bender = Forall.bend({'b': S('a')})
bender(source)  # -> [{'b': 23}, {'b': 27}]
```