Tl;dr lang- must be lowercase, capitalization on the language name can be anything

Let's try it out in the formatting sandbox:

All lowercase:

```lang-python
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

All caps:

```LANG-PYTHON
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

Language name all caps:

```lang-PYTHON
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

All mixed caps:

```LaNg-PyThOn
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

Language name mixed caps:

```lang-PYTHON
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

Tl;dr lang- must be lowercase, capitalization on the language name can be anything

Let's try it out in the formatting sandbox:

All lowercase:

```lang-python
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

All caps:

```LANG-PYTHON
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

Language name all caps:

```lang-PYTHON
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

All mixed caps:

```LaNg-PyThOn
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)

Language name mixed caps:

```lang-PyThOn
for i in range(10):
    if i % 2:
        print(i)
```

for i in range(10):
    if i % 2:
        print(i)