code: def _check_expression(expr):
      """Make sure an expression is not an empty string
  
      Parameters
      ----------
      expr : object
          An object that can be converted to a string
  
      Raises
      ------
      ValueError
        * If expr is an empty string
      """
      if not expr:
          raise ValueError("expr cannot be an empty string")
  
file_path: catboost/contrib/python/pandas/py2/pandas/core/computation/eval.py
imports: import tokenize
  import warnings
  from pandas.compat import string_types
  from pandas.util._validators import validate_bool_kwarg
  from pandas.core.computation.engines import _engines
  from pandas.core.computation.scope import _ensure_scope
  from pandas.io.formats.printing import pprint_thing
label_desc: Use image node_id 4 for calling a global function with example usage: _check_expression(expr) without return types