docs: def _varname_flow(self):
          """Build variable names for Pij, Pji, Qij, Qji, Sij, Sji"""
          if not self.n:
              return
  
          mpq = self.system.dae.m + 2 * self.system.Bus.n
          nl = self.n
  
          # Pij
          xy_idx = range(mpq, mpq + nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Pij',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='P_{ij}',
              element_name=self.name)
  
          # Pji
          xy_idx = range(mpq + nl, mpq + 2 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Pji',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='P_{ji}',
              element_name=self.name)
  
          # Qij
          xy_idx = range(mpq + 2 * nl, mpq + 3 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Qij',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='Q_{ij}',
              element_name=self.name)
  
          # Qji
          xy_idx = range(mpq + 3 * nl, mpq + 4 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Qji',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='Q_{ji}',
              element_name=self.name)
  
          # Iij Real
          xy_idx = range(mpq + 4 * nl, mpq + 5 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Iij_Re',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='\\Re(I_{ij})',
              element_name=self.name)
  
          # Iij Imag
          xy_idx = range(mpq + 5 * nl, mpq + 6 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Iij_Im',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='\\Im(I_{ij})',
              element_name=self.name)
  
          # Iji Real
          xy_idx = range(mpq + 6 * nl, mpq + 7 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Iji_Re',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='\\Re(I_{ji})',
              element_name=self.name)
  
          # Iji Imag
          xy_idx = range(mpq + 7 * nl, mpq + 8 * nl)
          self.system.varname.append(
              listname='unamey',
              xy_idx=xy_idx,
              var_name='Iji_Im',
              element_name=self.name)
          self.system.varname.append(
              listname='fnamey',
              xy_idx=xy_idx,
              var_name='\\Im(I_{ji})',
              element_name=self.name)