parameters: (self)
return_statement: return self.__transaction
docstring: Begin a nested transaction and return a transaction handle.
  
          The returned object is an instance of :class:`.NestedTransaction`.
  
          Nested transactions require SAVEPOINT support in the
          underlying database.  Any transaction in the hierarchy may
          ``commit`` and ``rollback``, however the outermost transaction
          still controls the overall ``commit`` or ``rollback`` of the
          transaction of a whole.
  
          .. seealso::
  
              :meth:`.Connection.begin`
  
              :meth:`.Connection.begin_twophase`
docstring_summary: Begin a nested transaction and return a transaction handle.
docstring_tokens: Begin a nested transaction and return a transaction handle .
function: def begin_nested(self):
          """Begin a nested transaction and return a transaction handle.
  
          The returned object is an instance of :class:`.NestedTransaction`.
  
          Nested transactions require SAVEPOINT support in the
          underlying database.  Any transaction in the hierarchy may
          ``commit`` and ``rollback``, however the outermost transaction
          still controls the overall ``commit`` or ``rollback`` of the
          transaction of a whole.
  
          .. seealso::
  
              :meth:`.Connection.begin`
  
              :meth:`.Connection.begin_twophase`
  
          """
          if self.__branch_from:
              return self.__branch_from.begin_nested()
  
          if self.__transaction is None:
              self.__transaction = RootTransaction(self)
          else:
              self.__transaction = NestedTransaction(self, self.__transaction)
          return self.__transaction
function_tokens: def begin_nested ( self ) : if self . __branch_from : return self . __branch_from . begin_nested ( ) if self . __transaction is None : self . __transaction = RootTransaction ( self ) else : self . __transaction = NestedTransaction ( self , self . __transaction ) return self . __transaction