class_docstr: Implements the *TextRank* algorithm defined by
  [[mihalcea04textrank]](https://derwen.ai/docs/ptr/biblio/#mihalcea04textrank),
  deployed as a `spaCy` pipeline component.
  
  This class does not get called directly; instantiate its factory
  instead.
      
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docstr: Construct the
  [*lemma graph*](https://derwen.ai/docs/ptr/glossary/#lemma-graph).
  
      returns:
  a directed graph representing the lemma graph
          
code: def _construct_graph(self) -> nx.DiGraph:
      """
      Construct the
      [*lemma graph*](https://derwen.ai/docs/ptr/glossary/#lemma-graph).
  
          returns:
      a directed graph representing the lemma graph
      """
      g = nx.DiGraph()
  
      # add nodes made of Lemma(lemma, pos)
      g.add_nodes_from(self.node_list)
  
      # add edges between nodes that co-occur within a window,
      # weighted by the count
      g.add_edges_from(self.edge_list)
  
      return g
  
imports: from collections import Counter, defaultdict, OrderedDict
  from dataclasses import dataclass
  import json
  import math
  import pathlib
  import time
  import typing
  from icecream import ic
  from spacy.tokens import Doc, Span, Token
  import graphviz
  import networkx
  from .util import groupby_apply, default_scrubber
label_desc: Use image node_id 5 for calling the BaseTextRank obj's underlying member method code with example usage: obj._construct_graph() and returns: g