code: func (c *Commit) Parent(i int) (*Commit, error) {
  	if len(c.ParentHashes) == 0 || i > len(c.ParentHashes)-1 {
  		return nil, ErrParentNotFound
  	}
  
  	return GetCommit(c.s, c.ParentHashes[i])
  }
docs: // Parent returns the ith parent of a commit.