re-addition of script

sequence_extractor/polyA.py

+import numpy as np
+# To do: Taking probabilities of nucleotides from user and raising error if sum != 1
+def PolyA_generator(
+	exon: str,
+) -> str:
+	"""Adds a PolyA tail to an exon sequence input into the function.
+
+	 Args:
+		exon: RNA sequence, obtained from concatenation of exons, that needs polyA to be added to its 3' end.
+
+	Returns:
+		RNA with polyA tail added to its 3' end.
+	"""
+	listA = ['A','T','G','C']
+	polyA = ''.join(np.random.choice(listA,250,p=[0.9,0.040,0.020,0.020]))
+	return (exon+polyA)