code: def remove_variable(self, v):
          
          if v not in self:
              return
  
          adj = self.adj
  
          # first remove all the interactions associated with v
          while adj[v]:
              self.remove_interaction(v, next(iter(adj[v])))
  
          # remove the variable
          del self.linear[v]
  
          try:
              # invalidates counterpart
              del self._counterpart
              if self.vartype is not Vartype.BINARY and hasattr(self, '_binary'):
                  del self._binary
              elif self.vartype is not Vartype.SPIN and hasattr(self, '_spin'):
                  del self._spin
          except AttributeError:
              pass
docs: Remove variable v and all its interactions from a binary quadratic model.
  
          Args:
              v (variable):
                  The variable to be removed from the binary quadratic model.
  
          Notes:
              If the specified variable is not in the binary quadratic model, this function does nothing.
  
          Examples:
              This example creates an Ising model and then removes one variable.
  
              >>> import dimod
              ...
              >>> bqm = dimod.BinaryQuadraticModel({'a': 0.0, 'b': 1.0, 'c': 2.0},
              ...                            {('a', 'b'): 0.25, ('a','c'): 0.5, ('b','c'): 0.75},
              ...                            -0.5, dimod.SPIN)
              >>> bqm.remove_variable('a')
              >>> 'a' in bqm.linear
              False
              >>> ('b','c') in bqm.quadratic
              True