code: def _expand_placeholder_value(value):
          
          if isinstance(value, (list, set)) or (isinstance(value, tuple) and len(value) != 1):
              sql_value = ','.join( [ RdbmsConnection._to_sql_value(
                          element if not isinstance(element, tuple) else element[0],
                          noquote=isinstance(element, tuple))
                      for element in value ])
  
          elif isinstance(value, tuple):
              assert len(value) == 1
              value = value[0]
              assert value is None or isinstance(value, basestring), 'basestring expected instead of %s' % type(value)
              sql_value = RdbmsConnection._to_sql_value(value, True)
  
          else:
              sql_value = RdbmsConnection._to_sql_value(value)
  
          return sql_value
docs: Return the SQL string representation of the specified placeholder's
          value.
  
  
          @param value: the value of a placeholder such as a simple element, a
              list, or a tuple of one string.
  
  
          @note: by convention, a tuple of one string indicates that this string
              MUST not be quoted as it represents, for instance, a called to
              a stored procedure, and not a textual content to modify into a
              table.
  
  
          @return: a SQL string representation.