Currently we're not checking if a key matches a pattern before we try to unmangle it.

For example, we have the following MANGLER pattern,

MANGLER:
  class: StringMatcher
  prefix: datadump-
  patterns:
    - action-*
    - apihelp-*

While importing, this should add datadump- prefix to any messages that begin with action- or apihelp-, and similarly when exporting it should only un-mangle those keys, and remove the datadump- prefix, but during export, it un-mangles all keys that start with datadump-.