class_docstr: User-facing catalog API, accessible through `SparkSession.catalog`.
  
  This is a thin wrapper around its Scala implementation org.apache.spark.sql.catalog.Catalog.
  
  .. versionchanged:: 3.4.0
      Supports Spark Connect.
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docstr: Check if the function with the specified name exists.
  This can either be a temporary function or a function.
  
  .. versionadded:: 3.3.0
  
  Parameters
  ----------
  functionName : str
      name of the function to check existence
  
      .. versionchanged:: 3.4.0
         Allow ``functionName`` to be qualified with catalog name
  
  dbName : str, optional
      name of the database to check function existence in.
  
  Returns
  -------
  bool
      Indicating whether the function exists
  
  Notes
  -----
  If no database is specified, the current database and catalog
  are used. This API includes all temporary functions.
  
  Examples
  --------
  >>> spark.catalog.functionExists("count")
  True
  
  Using the fully qualified name for function name.
  
  >>> spark.catalog.functionExists("default.unexisting_function")
  False
  >>> spark.catalog.functionExists("spark_catalog.default.unexisting_function")
  False
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code: def functionExists(
      self, functionName: str, dbName: Optional[str] = None
  ) -> bool:
      """Check if the function with the specified name exists.
      This can either be a temporary function or a function.
  
      .. versionadded:: 3.3.0
  
      Parameters
      ----------
      functionName : str
          name of the function to check existence
  
          .. versionchanged:: 3.4.0
             Allow ``functionName`` to be qualified with catalog name
  
      dbName : str, optional
          name of the database to check function existence in.
  
      Returns
      -------
      bool
          Indicating whether the function exists
  
      Notes
      -----
      If no database is specified, the current database and catalog
      are used. This API includes all temporary functions.
  
      Examples
      --------
      >>> spark.catalog.functionExists("count")
      True
  
      Using the fully qualified name for function name.
  
      >>> spark.catalog.functionExists("default.unexisting_function")
      False
      >>> spark.catalog.functionExists("spark_catalog.default.unexisting_function")
      False
      """
      if dbName is None:
          return self._jcatalog.functionExists(functionName)
      else:
          warnings.warn(
              "`dbName` has been deprecated since Spark 3.4 and might be removed in "
              "a future version. Use functionExists(`dbName.tableName`) instead.",
              FutureWarning,
          )
          return self._jcatalog.functionExists(dbName, functionName)
  
imports: import sys
  import warnings
  from typing import Any, Callable, NamedTuple, List, Optional, TYPE_CHECKING
  from pyspark.errors import PySparkTypeError
  from pyspark.storagelevel import StorageLevel
  from pyspark.sql.dataframe import DataFrame
  from pyspark.sql.session import SparkSession
  from pyspark.sql.types import StructType
label_desc: Use image node_id 13 for calling the Catalog obj's underlying member method code with example usage: obj.functionExists(functionName, dbName) and returns: self, self