How can I do a line break (line continuation) in Python (split up a long line of source code)?

Given:

e = 'a' + 'b' + 'c' + 'd'

How do I write the above in two lines?

e = 'a' + 'b' +
    'c' + 'd'

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_{See also: How do I split the definition of a long string over multiple lines? if there is a long string literal in the code that needs to be broken up to wrap the line nicely.}