Multiple adjacent string literals (delimited by whitespace),
possibly using different quoting conventions, are allowed, and
their meaning is the same as their concatenation. Thus, "hello"
'world' is equivalent to "helloworld". This feature can be used
to reduce the number of backslashes needed, to split long
strings conveniently across long lines, or even to add comments
to parts of strings, for example: re.compile("[A-Za-z_]" #
letter or underscore "[A-Za-z0-9_]*" # letter, digit or
underscore ) Note that this feature is defined at the
syntactical level, but implemented at compile time. The `+'
operator must be used to concatenate string expressions at run
time. Also note that literal concatenation can use different
quoting styles for each component (even mixing raw strings and
triple quoted strings).