convert alphanumeric phone number

phone_char_mappings = {
    'A': '2', 'B': '2', 'C': '2', 
    'D': '3', 'E': '3', 'F': '3',
    'G': '4', 'H': '4', 'I': '4',
    'J': '5', 'K': '5', 'L': '5',
    'M': '6', 'N': '6', 'O': '6',
    'P': '7', 'R': '7', 'S': '7',
    'T': '8', 'U': '8', 'V': '8',
    'W': '9', 'X': '9', 'Y': '9',
    '1': '1', '2': '2', '3': '3',
    '4': '4', '5': '5', '6': '6',
    '7': '7', '8': '8', '9': '9',
    '0': '0'
}

def alpha_phone_to_numeric(phone_number):
    return "".join([_convert_phone_char(char) for char in list(phone_number)])[:10]
    
def _convert_phone_char(char):
    if char in phone_char_mappings:
        return phone_char_mappings[char]
    else:
        return ''