code: def _interleaved_dtype(
          blocks: List[Block]
  ) -> Optional[Union[np.dtype, ExtensionDtype]]:
      
      if not len(blocks):
          return None
  
      return find_common_type([b.dtype for b in blocks])
docs: Find the common dtype for `blocks`.
  
      Parameters
      ----------
      blocks : List[Block]
  
      Returns
      -------
      dtype : Optional[Union[np.dtype, ExtensionDtype]]
          None is returned when `blocks` is empty.