import re

def processArray(array):
    newArray = []
    for l in array:
        m = re.findall(r"\[(.*?)]", " ".join(l))
        for n in m:
        	k = re.findall(r'[A-Za-z0-9+-]+', n)
        	if k:
        	    newArray.extend(k)
    return newArray

print(processArray([['Preconditions [+Here]\n'], ['Preconditions [+Is', '+The]\n'], ['Preconditions [-Example]\n']]))