code: def rand(
      seed: Union[int, Expression[int]] = None
  ) -> Expression[float]:
      """
      Returns a pseudorandom double value between 0.0 (inclusive) and 1.0 (exclusive) with a
      initial seed if specified. Two rand() functions will return identical sequences of numbers if
      they have same initial seed.
      """
      if seed is None:
          return _leaf_op("rand")
      else:
          return _unary_op("rand", seed)
  
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 37 for calling a global function with example usage: rand(seed) and returns: _leaf_op, _unary_op