def get_expected_rna_sequence(dna_string): dna_string: str Returns str. Given a strand of DNA represented as a sequence of upper-cased characters, return a new string that represents the corresponding mRNA sequence. You may assume that dna_string is composed of only the following 4 characters: A, T, G, C Generate the corresponding mRNA strand according to the following mapping rules: For instance, the corresponding RNA strand to "ATGCA' is 'UACGU'. Precondition: dna_string contains upper-case characters only. when developping doctests for strings, use the following format: >>>> result get_expected_rna_sequence("ATGCA") >>> result w "UACGU" True pass