class_docstr: Basic topological (non-weighted) directed Graph class
  
  Member variables:
  
  * V (int > 0): the number of vertices
  * E (int >= 0): the number of edges
  
  Properties:
  
  * vertices (list, type=int, shape=(V,))  vertices id
  * edges (list, type=int, shape=(E,2)): edges as vertices id tuples
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docstr: Returns the indexes of the vertices within the main cc
  
  Returns
  -------
  idx: array of shape (sizeof main cc)
docstr_tok: ["Returns","the","indexes","of","the","vertices","within","the","main","cc","Returns","--","--","--","-","idx",":","array","of","shape","(","sizeof","main","cc",")"]
code: def main_cc(self):
      """Returns the indexes of the vertices within the main cc
  
      Returns
      -------
      idx: array of shape (sizeof main cc)
      """
      if self.E > 0:
          cc = self.cc()
          pop = np.array([np.sum(cc == k) for k in np.unique(cc)])
          idx = np.nonzero(cc == pop.argmax())[0]
      else:
          idx = 0
      return idx
  
imports: import numpy
  from scipy.sparse import coo_matrix
label_desc: Use image node_id 12 for calling the Graph obj's underlying member method code with example usage: obj.main_cc() and returns: idx