code: def source_watermark() -> Expression:
      """
      Source watermark declaration for schema.
  
      This is a marker function that doesn't have concrete runtime implementation. It can only
      be used as a single expression for watermark strategies in schema declarations. The declaration
      will be pushed down into a table source that implements the `SupportsSourceWatermark`
      interface. The source will emit system-defined watermarks afterwards.
  
      Please check the documentation whether the connector supports source watermarks.
      """
      return _leaf_op("sourceWatermark")
  
imports: from typing import Union
  from pyflink import add_version_doc
  from pyflink.java_gateway import get_gateway
  from pyflink.table.expression import Expression, _get_java_expression, TimePointUnit, JsonOnNull
  from pyflink.table.types import _to_java_data_type, DataType
  from pyflink.table.udf import UserDefinedFunctionWrapper
  from pyflink.util.java_utils import to_jarray, load_java_class
label_desc: Use image node_id 46 for calling a global function with example usage: source_watermark() and returns: _leaf_op