<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def to_query(self, fields=None):
 """ Return a Query for this Table. Args: fields: the fields to return. If None, all fields will be returned. This can be a string which will be injected into the Query after SELECT, or a list of field names. Returns: A Query object that will return the specified fields from the records in the Table. """

    # Do import here to avoid top-level circular dependencies.
    from . import _query
    if fields is None:
      fields = '*'
    elif isinstance(fields, list):
      fields = ','.join(fields)
    return _query.Query('SELECT %s FROM %s' % (fields, self._repr_sql_()), context=self._context)