docs: def agent_key_info_from_key_id(key_id):
      """Find a matching key in the ssh-agent.
  
      @param key_id {str} Either a private ssh key fingerprint, e.g.
          'b3:f0:a1:6c:18:3b:42:63:fd:6e:57:42:74:17:d4:bc', or the path to
          an ssh private key file (like ssh's IdentityFile config option).
      @return {dict} with these keys:
          - type: "agent"
          - agent_key: paramiko AgentKey
          - fingerprint: key fingerprint
          - algorithm: "rsa-sha1"  Currently don't support DSA agent signing.
      """
      # Need the fingerprint of the key we're using for signing. If it
      # is a path to a priv key, then we need to load it.
      if not FINGERPRINT_RE.match(key_id):
          ssh_key = load_ssh_key(key_id, True)
          fingerprint = ssh_key["fingerprint"]
      else:
          fingerprint = key_id
  
      # Look for a matching fingerprint in the ssh-agent keys.
      keys = Agent().get_keys()
  
      for key in keys:
          raw_key = key.blob
  
  
          # The MD5 fingerprint functions return the hexdigest without the hash
          # algorithm prefix ("MD5:"), and the SHA256 functions return the
          # fingerprint with the prefix ("SHA256:").  Ideally we'd want to
          # normalize these, but more importantly we don't want to break backwards
          # compatibility for either the SHA or MD5 users.
          md5_fp = fingerprint_from_raw_ssh_pub_key(raw_key)
          sha_fp = sha256_fingerprint_from_raw_ssh_pub_key(raw_key)
          if (sha_fp == fingerprint or
              md5_fp == fingerprint or
              "MD5:" + md5_fp == fingerprint):
  
              # Canonicalize it to the md5 fingerprint.
              md5_fingerprint = md5_fp
              break
      else:
          raise MantaError('no ssh-agent key with fingerprint "%s"' %
                           fingerprint)
  
      return {
          "type": "agent",
          "agent_key": key,
          "fingerprint": md5_fingerprint,
          "algorithm": ALGO_FROM_SSH_KEY_TYPE[key.name]
      }