import pandas as pd

# Create a new dataframe named target_df
target_df = pd.DataFrame()

# Copy the 'case_date' column from source_df to the 'CaseDate' column in target_df without any transformation
target_df["CaseDate"] = source_df["case_date"]

# Concatenate the 'firstname' and 'lastname' columns from source_df (with a space in between) and store the result in the 'FullName' column in target_df
target_df["FullName"] = source_df["firstname"] + " " + source_df["lastname"]

# Copy the 'case_type' column from source_df to the 'CaseType' column in target_df without any transformation
target_df["CaseType"] = source_df["case_type"]

# Return the target_df as the output of the script
target_df