class_docstr: A Cell serves a Direct Acyclic Graph (DAG) which holds blocks as nodes and edges that
  connects operation paths between the nodes.
class_docstr_tok: ["A","Cell","serves","a","Direct","Acyclic","Graph","(","DAG",")","which","holds","blocks","as","nodes","and","edges","that","connects","operation","paths","between","the","nodes","."]
docstr: Whether cell is valid or not.
docstr_tok: ["Whether","cell","is","valid","or","not","."]
code: def valid(self) -> bool:
      """Whether cell is valid or not."""
  
      if self.input_idx == -1 or self.output_idx == -1:
          return False
  
      return nx.is_directed_acyclic_graph(self)
  
file_path: opytimizer/opytimizer/core/cell.py
imports: import copy
  from typing import Generator, Tuple
  import networkx
  from networkx import DiGraph
  from opytimizer.core import InnerBlock, InputBlock, OutputBlock
  from opytimizer.core.block import Block
label_desc: Use image node_id 5 for calling the Cell obj's underlying member method code with example usage: obj.valid() and returns: nx, False