code: def get_keys(keyfiles, signature_type):
      
      builtin_keys = {
          ('release', 'sha1'): [mardor.mozilla.release1_sha1, mardor.mozilla.release2_sha1],
          ('release', 'sha384'): [mardor.mozilla.release1_sha384, mardor.mozilla.release2_sha384],
          ('nightly', 'sha1'): [mardor.mozilla.nightly1_sha1, mardor.mozilla.nightly2_sha1],
          ('nightly', 'sha384'): [mardor.mozilla.nightly1_sha384, mardor.mozilla.nightly2_sha384],
          ('dep', 'sha1'): [mardor.mozilla.dep1_sha1, mardor.mozilla.dep2_sha1],
          ('dep', 'sha384'): [mardor.mozilla.dep1_sha384, mardor.mozilla.dep2_sha384],
          ('autograph-stage', 'sha384'): [mardor.mozilla.autograph_stage_sha384],
      }
      keys = []
      for keyfile in keyfiles:
          if keyfile.startswith(':mozilla-'):
              name = keyfile.split(':mozilla-')[1]
              try:
                  keys.extend(builtin_keys[name, signature_type])
              except KeyError:
                  raise ValueError('Invalid internal key name: {}'
                                   .format(keyfile))
          else:
              key = open(keyfile, 'rb').read()
              keys.append(key)
      return keys
docs: Get public keys for the given keyfiles.
  
      Args:
          keyfiles: List of filenames with public keys, or :mozilla- prefixed key
                    names
          signature_type: one of 'sha1' or 'sha384'
  
      Returns:
          List of public keys as strings