code: def merge_dicts(a, b):
      merges b into a"""
  
      for key in b:
          if key in a:
              if isinstance(a[key], dict) and isinstance(b[key], dict):
                  merge_dicts(a[key], b[key])
              else:
                  a[key] = b[key]
          else:
              a[key] = b[key]
  
      return a
docs: merges b into a