Error when no column adheres to reg_ex with Pyspark SQL DataFrameModel: 'list' object has no attribute 'tolist'

[PabloHervadaSDG]

Describe the bug
When validating a pyspark dataframe using DataFrameModel with Pysaprk SQL, if there is a regular expression that is not met by any column of the dataframe, pandera can't validate the df, due to a bug handling the list of columns that match the reg_ex, it seems.

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of pandera.
• (optional) I have confirmed this bug exists on the main branch of pandera.

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Code Sample, a copy-pastable example

from pyspark.sql import SparkSession
import pyspark.sql.types as T
import pandera.pyspark as pa

# Create a example dataframe
spark = SparkSession.builder.master("local").appName("pyspark-pandera").getOrCreate()

schema = T.StructType([
    T.StructField("user_name", T.StringType(), True),
    T.StructField("email", T.StringType(), True)
])

data = [
    ("Alice", "[email protected]"),
    ("Bob", "[email protected]"),
]

df = spark.createDataFrame(data, schema)

# Validate dataframe with Pandera DataFrameModel
class ExampleModel(pa.DataFrameModel):
    user_name: T.StringType() = pa.Field(nullable=False)
    # There is no field that matches this reg_ex
    age_field: T.IntegerType() = pa.Field(alias="(.+)age(.+)", regex=True)

df_out = ExampleModel.validate(df)

Expected behavior

I expect df to be validated, and df_out to contain all the errors with the dataframe, according to the dataframe model.
In contrast, ExampleModel.validate(df) leads to an error handling the reg_ex columns:

AttributeError: 'list' object has no attribute 'tolist'

Desktop (please complete the following information):

• OS: Windows 11
• Browser: Chrome
• Version: Pandera version 0.20.3

Screenshots